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 $88.41   8.645%   $96.053   $96.05   $96.05   $96.10  
  Purchase #2 $123.84   3.189%   $127.7893   $127.79   $127.80   $127.80  
  Purchase #3 $233.52   5.788%   $247.0361   $247.04   $247.05   $247.00  
  Purchase #4 $112.28   13.344%   $127.2626   $127.26   $127.25   $127.30  
  Purchase #5 $102.29   8.462%   $110.9458   $110.95   $110.95   $110.90  
  Purchase #6 $83.29   3.536%   $86.2351   $86.24   $86.25   $86.20  
  Purchase #7 $204.88   6.420%   $218.0333   $218.03   $218.05   $218.00  
  7 purchase totals = $948.51       $1,013.3552   $1,013.36   $1,013.40   $1,013.30