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 $56.55   9.603%   $61.9805   $61.98   $62.00   $62.00  
  Purchase #2 $161.52   9.650%   $177.1067   $177.11   $177.10   $177.10  
  Purchase #3 $93.87   11.679%   $104.8331   $104.83   $104.85   $104.80  
  Purchase #4 $185.35   8.444%   $201.001   $201.00   $201.00   $201.00  
  Purchase #5 $192.52   11.808%   $215.2528   $215.25   $215.25   $215.30  
  Purchase #6 $170.59   8.223%   $184.6176   $184.62   $184.60   $184.60  
  Purchase #7 $241.79   3.603%   $250.5017   $250.50   $250.50   $250.50  
  7 purchase totals = $1,102.19       $1,195.2934   $1,195.29   $1,195.30   $1,195.30