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 $182.82   5.361%   $192.621   $192.62   $192.60   $192.60  
  Purchase #2 $44.33   5.226%   $46.6467   $46.65   $46.65   $46.60  
  Purchase #3 $51.48   3.328%   $53.1933   $53.19   $53.20   $53.20  
  Purchase #4 $247.67   11.445%   $276.0158   $276.02   $276.00   $276.00  
  Purchase #5 $169.35   11.415%   $188.6813   $188.68   $188.70   $188.70  
  Purchase #6 $82.71   5.822%   $87.5254   $87.53   $87.55   $87.50  
  Purchase #7 $89.59   5.657%   $94.6581   $94.66   $94.65   $94.70  
  7 purchase totals = $867.95       $939.3416   $939.35   $939.35   $939.30