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 $211.70   10.155%   $233.1981   $233.20   $233.20   $233.20  
  Purchase #2 $217.53   12.419%   $244.5451   $244.55   $244.55   $244.50  
  Purchase #3 $59.52   12.777%   $67.1249   $67.12   $67.10   $67.10  
  Purchase #4 $216.93   10.588%   $239.8985   $239.90   $239.90   $239.90  
  Purchase #5 $20.80   8.202%   $22.506   $22.51   $22.50   $22.50  
  Purchase #6 $158.95   11.618%   $177.4168   $177.42   $177.40   $177.40  
  Purchase #7 $158.33   12.213%   $177.6668   $177.67   $177.65   $177.70  
  7 purchase totals = $1,043.76       $1,162.3562   $1,162.37   $1,162.30   $1,162.30