Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $116.44   9.605%   $127.6241   $127.62   $127.60   $127.60  
  Purchase #2 $200.32   5.768%   $211.8745   $211.87   $211.85   $211.90  
  Purchase #3 $114.38   12.165%   $128.2943   $128.29   $128.30   $128.30  
  Purchase #4 $167.55   5.699%   $177.0987   $177.10   $177.10   $177.10  
  Purchase #5 $195.54   4.517%   $204.3725   $204.37   $204.35   $204.40  
  Purchase #6 $110.91   3.558%   $114.8562   $114.86   $114.85   $114.90  
  Purchase #7 $217.30   6.279%   $230.9443   $230.94   $230.95   $230.90  
  7 purchase totals = $1,122.44       $1,195.0646   $1,195.05   $1,195.00   $1,195.10