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 $238.27   5.313%   $250.9293   $250.93   $250.95   $250.90  
  Purchase #2 $77.36   8.216%   $83.7159   $83.72   $83.70   $83.70  
  Purchase #3 $214.82   12.279%   $241.1977   $241.20   $241.20   $241.20  
  Purchase #4 $246.90   11.237%   $274.6442   $274.64   $274.65   $274.60  
  Purchase #5 $219.57   4.594%   $229.657   $229.66   $229.65   $229.70  
  Purchase #6 $213.73   13.519%   $242.6242   $242.62   $242.60   $242.60  
  Purchase #7 $84.54   11.340%   $94.1268   $94.13   $94.15   $94.10  
  7 purchase totals = $1,295.19       $1,416.8951   $1,416.90   $1,416.90   $1,416.80