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 $95.63   6.345%   $101.6977   $101.70   $101.70   $101.70  
  Purchase #2 $141.39   8.210%   $152.9981   $153.00   $153.00   $153.00  
  Purchase #3 $24.71   4.820%   $25.901   $25.90   $25.90   $25.90  
  Purchase #4 $187.33   11.410%   $208.7044   $208.70   $208.70   $208.70  
  Purchase #5 $71.29   5.464%   $75.1853   $75.19   $75.20   $75.20  
  Purchase #6 $223.48   12.332%   $251.0396   $251.04   $251.05   $251.00  
  Purchase #7 $111.48   6.315%   $118.52   $118.52   $118.50   $118.50  
  7 purchase totals = $855.31       $934.0461   $934.05   $934.05   $934.00