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 $59.66   3.535%   $61.769   $61.77   $61.75   $61.80  
  Purchase #2 $84.65   11.649%   $94.5109   $94.51   $94.50   $94.50  
  Purchase #3 $29.80   5.170%   $31.3407   $31.34   $31.35   $31.30  
  Purchase #4 $47.58   10.321%   $52.4907   $52.49   $52.50   $52.50  
  Purchase #5 $195.77   5.361%   $206.2652   $206.27   $206.25   $206.30  
  Purchase #6 $15.69   5.570%   $16.5639   $16.56   $16.55   $16.60  
  Purchase #7 $58.30   10.572%   $64.4635   $64.46   $64.45   $64.50  
  7 purchase totals = $491.45       $527.4039   $527.40   $527.35   $527.50