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 $219.25   11.753%   $245.0185   $245.02   $245.00   $245.00  
  Purchase #2 $33.68   4.762%   $35.2838   $35.28   $35.30   $35.30  
  Purchase #3 $59.65   11.516%   $66.5193   $66.52   $66.50   $66.50  
  Purchase #4 $23.38   10.322%   $25.7933   $25.79   $25.80   $25.80  
  Purchase #5 $230.94   11.775%   $258.1332   $258.13   $258.15   $258.10  
  Purchase #6 $202.54   6.626%   $215.9603   $215.96   $215.95   $216.00  
  Purchase #7 $239.97   13.550%   $272.4859   $272.49   $272.50   $272.50  
  7 purchase totals = $1,009.41       $1,119.1943   $1,119.19   $1,119.20   $1,119.20