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 $44.41   9.551%   $48.6516   $48.65   $48.65   $48.70  
  Purchase #2 $54.46   11.802%   $60.8874   $60.89   $60.90   $60.90  
  Purchase #3 $39.45   7.859%   $42.5504   $42.55   $42.55   $42.60  
  Purchase #4 $208.39   4.283%   $217.3153   $217.32   $217.30   $217.30  
  Purchase #5 $218.40   13.255%   $247.3489   $247.35   $247.35   $247.30  
  Purchase #6 $32.74   11.131%   $36.3843   $36.38   $36.40   $36.40  
  Purchase #7 $143.52   3.156%   $148.0495   $148.05   $148.05   $148.00  
  7 purchase totals = $741.37       $801.1874   $801.19   $801.20   $801.20