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 $245.67   9.111%   $268.053   $268.05   $268.05   $268.10  
  Purchase #2 $91.99   8.332%   $99.6546   $99.65   $99.65   $99.70  
  Purchase #3 $123.58   3.541%   $127.956   $127.96   $127.95   $128.00  
  Purchase #4 $30.44   11.469%   $33.9312   $33.93   $33.95   $33.90  
  Purchase #5 $203.60   6.192%   $216.2069   $216.21   $216.20   $216.20  
  Purchase #6 $211.57   6.390%   $225.0893   $225.09   $225.10   $225.10  
  Purchase #7 $101.33   4.630%   $106.0216   $106.02   $106.00   $106.00  
  7 purchase totals = $1,008.18       $1,076.9126   $1,076.91   $1,076.90   $1,077.00