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 $87.63   6.804%   $93.5923   $93.59   $93.60   $93.60  
  Purchase #2 $174.43   12.741%   $196.6541   $196.65   $196.65   $196.70  
  Purchase #3 $23.86   9.251%   $26.0673   $26.07   $26.05   $26.10  
  Purchase #4 $41.73   10.754%   $46.2176   $46.22   $46.20   $46.20  
  Purchase #5 $46.33   5.847%   $49.0389   $49.04   $49.05   $49.00  
  Purchase #6 $149.79   10.751%   $165.8939   $165.89   $165.90   $165.90  
  Purchase #7 $150.47   3.710%   $156.0524   $156.05   $156.05   $156.10  
  7 purchase totals = $674.24       $733.5165   $733.51   $733.50   $733.60