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 $185.78   8.741%   $202.019   $202.02   $202.00   $202.00  
  Purchase #2 $99.77   3.747%   $103.5084   $103.51   $103.50   $103.50  
  Purchase #3 $41.74   10.203%   $45.9987   $46.00   $46.00   $46.00  
  Purchase #4 $240.57   8.362%   $260.6865   $260.69   $260.70   $260.70  
  Purchase #5 $237.29   5.784%   $251.0149   $251.01   $251.00   $251.00  
  Purchase #6 $121.34   9.318%   $132.6465   $132.65   $132.65   $132.60  
  Purchase #7 $61.46   6.303%   $65.3338   $65.33   $65.35   $65.30  
  7 purchase totals = $987.95       $1,061.2078   $1,061.21   $1,061.20   $1,061.10