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 $54.82   10.816%   $60.7493   $60.75   $60.75   $60.70  
  Purchase #2 $226.82   6.818%   $242.2846   $242.28   $242.30   $242.30  
  Purchase #3 $47.92   3.716%   $49.7007   $49.70   $49.70   $49.70  
  Purchase #4 $48.37   4.771%   $50.6777   $50.68   $50.70   $50.70  
  Purchase #5 $236.26   4.543%   $246.9933   $246.99   $247.00   $247.00  
  Purchase #6 $67.68   11.423%   $75.4111   $75.41   $75.40   $75.40  
  Purchase #7 $212.70   6.320%   $226.1426   $226.14   $226.15   $226.10  
  7 purchase totals = $894.57       $951.9593   $951.95   $952.00   $951.90