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 $199.65   5.706%   $211.042   $211.04   $211.05   $211.00  
  Purchase #2 $109.45   8.858%   $119.1451   $119.15   $119.15   $119.10  
  Purchase #3 $33.95   6.159%   $36.041   $36.04   $36.05   $36.00  
  Purchase #4 $189.92   5.540%   $200.4416   $200.44   $200.45   $200.40  
  Purchase #5 $103.87   10.280%   $114.5478   $114.55   $114.55   $114.50  
  Purchase #6 $198.27   3.663%   $205.5326   $205.53   $205.55   $205.50  
  Purchase #7 $176.92   3.635%   $183.351   $183.35   $183.35   $183.40  
  7 purchase totals = $1,012.03       $1,070.1011   $1,070.10   $1,070.15   $1,069.90