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 $105.29   12.586%   $118.5418   $118.54   $118.55   $118.50  
  Purchase #2 $216.58   13.733%   $246.3229   $246.32   $246.30   $246.30  
  Purchase #3 $131.79   7.541%   $141.7283   $141.73   $141.75   $141.70  
  Purchase #4 $243.88   10.178%   $268.7021   $268.70   $268.70   $268.70  
  Purchase #5 $187.68   11.365%   $209.0098   $209.01   $209.00   $209.00  
  Purchase #6 $87.78   9.708%   $96.3017   $96.30   $96.30   $96.30  
  Purchase #7 $62.41   7.294%   $66.9622   $66.96   $66.95   $67.00  
  7 purchase totals = $1,035.41       $1,147.5688   $1,147.56   $1,147.55   $1,147.50