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 $111.82   11.749%   $124.9577   $124.96   $124.95   $125.00  
  Purchase #2 $131.52   13.375%   $149.1108   $149.11   $149.10   $149.10  
  Purchase #3 $184.96   8.684%   $201.0219   $201.02   $201.00   $201.00  
  Purchase #4 $121.35   9.445%   $132.8115   $132.81   $132.80   $132.80  
  Purchase #5 $191.74   5.746%   $202.7574   $202.76   $202.75   $202.80  
  Purchase #6 $170.70   9.422%   $186.7834   $186.78   $186.80   $186.80  
  Purchase #7 $14.68   12.396%   $16.4997   $16.50   $16.50   $16.50  
  7 purchase totals = $926.77       $1,013.9424   $1,013.94   $1,013.90   $1,014.00