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 $43.47   6.517%   $46.3029   $46.30   $46.30   $46.30  
  Purchase #2 $242.26   11.241%   $269.4924   $269.49   $269.50   $269.50  
  Purchase #3 $110.67   6.555%   $117.9244   $117.92   $117.90   $117.90  
  Purchase #4 $222.49   6.760%   $237.5303   $237.53   $237.55   $237.50  
  Purchase #5 $228.76   6.428%   $243.4647   $243.46   $243.45   $243.50  
  Purchase #6 $194.39   6.599%   $207.2178   $207.22   $207.20   $207.20  
  Purchase #7 $39.85   13.714%   $45.315   $45.32   $45.30   $45.30  
  7 purchase totals = $1,081.89       $1,167.2475   $1,167.24   $1,167.20   $1,167.20