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 $63.87   12.569%   $71.8978   $71.90   $71.90   $71.90  
  Purchase #2 $165.82   6.381%   $176.401   $176.40   $176.40   $176.40  
  Purchase #3 $110.99   8.242%   $120.1378   $120.14   $120.15   $120.10  
  Purchase #4 $240.80   8.198%   $260.5408   $260.54   $260.55   $260.50  
  Purchase #5 $156.65   6.527%   $166.8745   $166.87   $166.85   $166.90  
  Purchase #6 $106.78   11.741%   $119.317   $119.32   $119.30   $119.30  
  Purchase #7 $177.34   10.120%   $195.2868   $195.29   $195.30   $195.30  
  7 purchase totals = $1,022.25       $1,110.4557   $1,110.46   $1,110.45   $1,110.40