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 $11.26   4.369%   $11.7519   $11.75   $11.75   $11.80  
  Purchase #2 $237.46   9.339%   $259.6364   $259.64   $259.65   $259.60  
  Purchase #3 $40.66   8.111%   $43.9579   $43.96   $43.95   $44.00  
  Purchase #4 $213.67   9.600%   $234.1823   $234.18   $234.20   $234.20  
  Purchase #5 $85.60   12.347%   $96.169   $96.17   $96.15   $96.20  
  Purchase #6 $123.94   3.864%   $128.729   $128.73   $128.75   $128.70  
  Purchase #7 $163.82   7.141%   $175.5184   $175.52   $175.50   $175.50  
  7 purchase totals = $876.41       $949.9449   $949.95   $949.95   $950.00