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 $58.58   4.305%   $61.1019   $61.10   $61.10   $61.10  
  Purchase #2 $69.46   10.350%   $76.6491   $76.65   $76.65   $76.60  
  Purchase #3 $91.64   6.302%   $97.4152   $97.42   $97.40   $97.40  
  Purchase #4 $245.39   11.163%   $272.7829   $272.78   $272.80   $272.80  
  Purchase #5 $29.53   8.785%   $32.1242   $32.12   $32.10   $32.10  
  Purchase #6 $243.87   5.141%   $256.4074   $256.41   $256.40   $256.40  
  Purchase #7 $199.86   13.212%   $226.2655   $226.27   $226.25   $226.30  
  7 purchase totals = $938.33       $1,022.7462   $1,022.75   $1,022.70   $1,022.70