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 $196.92   9.573%   $215.7712   $215.77   $215.75   $215.80  
  Purchase #2 $199.68   13.297%   $226.2314   $226.23   $226.25   $226.20  
  Purchase #3 $86.58   7.525%   $93.0951   $93.10   $93.10   $93.10  
  Purchase #4 $55.36   10.743%   $61.3073   $61.31   $61.30   $61.30  
  Purchase #5 $44.55   7.367%   $47.832   $47.83   $47.85   $47.80  
  Purchase #6 $80.72   13.688%   $91.769   $91.77   $91.75   $91.80  
  Purchase #7 $196.70   10.586%   $217.5227   $217.52   $217.50   $217.50  
  7 purchase totals = $860.51       $953.5287   $953.53   $953.50   $953.50