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 $114.58   3.872%   $119.0165   $119.02   $119.00   $119.00  
  Purchase #2 $210.42   6.299%   $223.6744   $223.67   $223.65   $223.70  
  Purchase #3 $164.49   11.491%   $183.3915   $183.39   $183.40   $183.40  
  Purchase #4 $31.50   13.369%   $35.7112   $35.71   $35.70   $35.70  
  Purchase #5 $174.74   3.729%   $181.2561   $181.26   $181.25   $181.30  
  Purchase #6 $221.92   10.650%   $245.5545   $245.55   $245.55   $245.60  
  Purchase #7 $155.49   7.244%   $166.7537   $166.75   $166.75   $166.80  
  7 purchase totals = $1,073.14       $1,155.3579   $1,155.35   $1,155.30   $1,155.50