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 $185.35   5.227%   $195.0382   $195.04   $195.05   $195.00  
  Purchase #2 $27.73   3.346%   $28.6578   $28.66   $28.65   $28.70  
  Purchase #3 $89.46   12.214%   $100.3866   $100.39   $100.40   $100.40  
  Purchase #4 $104.72   5.753%   $110.7445   $110.74   $110.75   $110.70  
  Purchase #5 $245.81   9.112%   $268.2082   $268.21   $268.20   $268.20  
  Purchase #6 $24.75   5.353%   $26.0749   $26.07   $26.05   $26.10  
  Purchase #7 $89.36   7.820%   $96.348   $96.35   $96.35   $96.30  
  7 purchase totals = $767.18       $825.4582   $825.46   $825.45   $825.40