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 $214.85   10.774%   $237.9979   $238.00   $238.00   $238.00  
  Purchase #2 $229.70   9.695%   $251.9694   $251.97   $251.95   $252.00  
  Purchase #3 $173.54   12.299%   $194.8837   $194.88   $194.90   $194.90  
  Purchase #4 $69.51   8.653%   $75.5247   $75.52   $75.50   $75.50  
  Purchase #5 $246.61   9.204%   $269.308   $269.31   $269.30   $269.30  
  Purchase #6 $67.96   13.115%   $76.873   $76.87   $76.85   $76.90  
  Purchase #7 $100.40   4.485%   $104.9029   $104.90   $104.90   $104.90  
  7 purchase totals = $1,102.57       $1,211.4596   $1,211.45   $1,211.40   $1,211.50