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 $67.43   12.745%   $76.024   $76.02   $76.00   $76.00  
  Purchase #2 $200.98   12.455%   $226.0121   $226.01   $226.00   $226.00  
  Purchase #3 $42.63   3.647%   $44.1847   $44.18   $44.20   $44.20  
  Purchase #4 $145.73   7.682%   $156.925   $156.93   $156.95   $156.90  
  Purchase #5 $64.34   12.190%   $72.183   $72.18   $72.20   $72.20  
  Purchase #6 $111.72   7.374%   $119.9582   $119.96   $119.95   $120.00  
  Purchase #7 $219.32   8.746%   $238.5017   $238.50   $238.50   $238.50  
  7 purchase totals = $852.15       $933.7887   $933.78   $933.80   $933.80