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 $222.54   9.654%   $244.024   $244.02   $244.00   $244.00  
  Purchase #2 $106.80   9.514%   $116.961   $116.96   $116.95   $117.00  
  Purchase #3 $170.69   6.672%   $182.0784   $182.08   $182.10   $182.10  
  Purchase #4 $236.31   11.549%   $263.6014   $263.60   $263.60   $263.60  
  Purchase #5 $187.56   7.734%   $202.0659   $202.07   $202.05   $202.10  
  Purchase #6 $230.41   9.340%   $251.9303   $251.93   $251.95   $251.90  
  Purchase #7 $22.81   7.398%   $24.4975   $24.50   $24.50   $24.50  
  7 purchase totals = $1,177.12       $1,285.1585   $1,285.16   $1,285.15   $1,285.20