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 $43.43   6.682%   $46.332   $46.33   $46.35   $46.30  
  Purchase #2 $188.95   7.759%   $203.6106   $203.61   $203.60   $203.60  
  Purchase #3 $111.62   5.114%   $117.3282   $117.33   $117.35   $117.30  
  Purchase #4 $70.89   4.753%   $74.2594   $74.26   $74.25   $74.30  
  Purchase #5 $115.91   5.163%   $121.8944   $121.89   $121.90   $121.90  
  Purchase #6 $108.97   11.163%   $121.1343   $121.13   $121.15   $121.10  
  Purchase #7 $246.64   11.847%   $275.8594   $275.86   $275.85   $275.90  
  7 purchase totals = $886.41       $960.4183   $960.41   $960.45   $960.40