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 $43.98   7.436%   $47.2504   $47.25   $47.25   $47.30  
  Purchase #2 $62.99   11.140%   $70.0071   $70.01   $70.00   $70.00  
  Purchase #3 $211.77   11.644%   $236.4285   $236.43   $236.45   $236.40  
  Purchase #4 $58.68   3.788%   $60.9028   $60.90   $60.90   $60.90  
  Purchase #5 $163.90   3.738%   $170.0266   $170.03   $170.05   $170.00  
  Purchase #6 $193.68   9.244%   $211.5838   $211.58   $211.60   $211.60  
  Purchase #7 $207.39   10.783%   $229.7529   $229.75   $229.75   $229.80  
  7 purchase totals = $942.39       $1,025.9521   $1,025.95   $1,026.00   $1,026.00