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 $85.40   12.355%   $95.9512   $95.95   $95.95   $96.00  
  Purchase #2 $228.32   6.564%   $243.3069   $243.31   $243.30   $243.30  
  Purchase #3 $101.41   11.647%   $113.2212   $113.22   $113.20   $113.20  
  Purchase #4 $236.90   13.306%   $268.4219   $268.42   $268.40   $268.40  
  Purchase #5 $125.42   13.551%   $142.4157   $142.42   $142.40   $142.40  
  Purchase #6 $31.57   12.709%   $35.5822   $35.58   $35.60   $35.60  
  Purchase #7 $245.84   7.690%   $264.7451   $264.75   $264.75   $264.70  
  7 purchase totals = $1,054.86       $1,163.6442   $1,163.65   $1,163.60   $1,163.60