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 $44.37   9.712%   $48.6792   $48.68   $48.70   $48.70  
  Purchase #2 $88.64   5.463%   $93.4824   $93.48   $93.50   $93.50  
  Purchase #3 $125.76   13.755%   $143.0583   $143.06   $143.05   $143.10  
  Purchase #4 $195.95   6.695%   $209.0689   $209.07   $209.05   $209.10  
  Purchase #5 $79.51   11.243%   $88.4493   $88.45   $88.45   $88.40  
  Purchase #6 $119.87   5.520%   $126.4868   $126.49   $126.50   $126.50  
  Purchase #7 $165.98   10.449%   $183.3233   $183.32   $183.30   $183.30  
  7 purchase totals = $820.08       $892.5482   $892.55   $892.55   $892.60