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 $97.46   4.243%   $101.5952   $101.60   $101.60   $101.60  
  Purchase #2 $229.96   10.740%   $254.6577   $254.66   $254.65   $254.70  
  Purchase #3 $83.26   3.544%   $86.2107   $86.21   $86.20   $86.20  
  Purchase #4 $247.95   4.499%   $259.1053   $259.11   $259.10   $259.10  
  Purchase #5 $62.76   3.185%   $64.7589   $64.76   $64.75   $64.80  
  Purchase #6 $146.43   12.144%   $164.2125   $164.21   $164.20   $164.20  
  Purchase #7 $93.89   8.492%   $101.8631   $101.86   $101.85   $101.90  
  7 purchase totals = $961.71       $1,032.4034   $1,032.41   $1,032.35   $1,032.50