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 $196.80   9.373%   $215.2461   $215.25   $215.25   $215.20  
  Purchase #2 $216.48   11.114%   $240.5396   $240.54   $240.55   $240.50  
  Purchase #3 $32.95   8.231%   $35.6621   $35.66   $35.65   $35.70  
  Purchase #4 $234.52   4.547%   $245.1836   $245.18   $245.20   $245.20  
  Purchase #5 $209.85   8.244%   $227.15   $227.15   $227.15   $227.20  
  Purchase #6 $91.50   11.872%   $102.3629   $102.36   $102.35   $102.40  
  Purchase #7 $93.93   8.793%   $102.1893   $102.19   $102.20   $102.20  
  7 purchase totals = $1,076.03       $1,168.3336   $1,168.33   $1,168.35   $1,168.40