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 $96.91   5.177%   $101.927   $101.93   $101.95   $101.90  
  Purchase #2 $188.52   3.243%   $194.6337   $194.63   $194.65   $194.60  
  Purchase #3 $32.77   11.186%   $36.4357   $36.44   $36.45   $36.40  
  Purchase #4 $98.39   5.748%   $104.0455   $104.05   $104.05   $104.00  
  Purchase #5 $162.93   4.392%   $170.0859   $170.09   $170.10   $170.10  
  Purchase #6 $233.30   8.294%   $252.6499   $252.65   $252.65   $252.60  
  Purchase #7 $24.48   3.638%   $25.3706   $25.37   $25.35   $25.40  
  7 purchase totals = $837.30       $885.1483   $885.16   $885.20   $885.00