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 $73.97   11.334%   $82.3538   $82.35   $82.35   $82.40  
  Purchase #2 $214.77   5.126%   $225.7791   $225.78   $225.80   $225.80  
  Purchase #3 $5.47   10.616%   $6.0507   $6.05   $6.05   $6.10  
  Purchase #4 $148.97   12.233%   $167.1935   $167.19   $167.20   $167.20  
  Purchase #5 $117.43   11.792%   $131.2773   $131.28   $131.30   $131.30  
  Purchase #6 $97.63   11.182%   $108.547   $108.55   $108.55   $108.50  
  Purchase #7 $37.55   10.181%   $41.373   $41.37   $41.35   $41.40  
  7 purchase totals = $695.79       $762.5744   $762.57   $762.60   $762.70