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 $213.96   10.793%   $237.0527   $237.05   $237.05   $237.10  
  Purchase #2 $56.56   7.859%   $61.0051   $61.01   $61.00   $61.00  
  Purchase #3 $41.87   10.121%   $46.1077   $46.11   $46.10   $46.10  
  Purchase #4 $69.49   7.109%   $74.43   $74.43   $74.45   $74.40  
  Purchase #5 $64.37   5.527%   $67.9277   $67.93   $67.95   $67.90  
  Purchase #6 $235.75   8.748%   $256.3734   $256.37   $256.35   $256.40  
  Purchase #7 $17.42   11.400%   $19.4059   $19.41   $19.40   $19.40  
  7 purchase totals = $699.42       $762.3025   $762.31   $762.30   $762.30