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 $162.26   12.751%   $182.9498   $182.95   $182.95   $182.90  
  Purchase #2 $43.38   8.345%   $47.0001   $47.00   $47.00   $47.00  
  Purchase #3 $47.30   3.237%   $48.8311   $48.83   $48.85   $48.80  
  Purchase #4 $112.88   9.117%   $123.1713   $123.17   $123.15   $123.20  
  Purchase #5 $107.28   10.346%   $118.3792   $118.38   $118.40   $118.40  
  Purchase #6 $124.45   11.498%   $138.7593   $138.76   $138.75   $138.80  
  Purchase #7 $199.67   8.414%   $216.4702   $216.47   $216.45   $216.50  
  7 purchase totals = $797.22       $875.5610   $875.56   $875.55   $875.60