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 $86.63   8.477%   $93.9736   $93.97   $93.95   $94.00  
  Purchase #2 $161.43   13.434%   $183.1165   $183.12   $183.10   $183.10  
  Purchase #3 $224.88   13.219%   $254.6069   $254.61   $254.60   $254.60  
  Purchase #4 $157.52   13.469%   $178.7364   $178.74   $178.75   $178.70  
  Purchase #5 $54.80   7.471%   $58.8941   $58.89   $58.90   $58.90  
  Purchase #6 $97.28   12.832%   $109.763   $109.76   $109.75   $109.80  
  Purchase #7 $226.25   7.785%   $243.8636   $243.86   $243.85   $243.90  
  7 purchase totals = $1,008.79       $1,122.9541   $1,122.95   $1,122.90   $1,123.00