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 $175.41   11.154%   $194.9752   $194.98   $195.00   $195.00  
  Purchase #2 $56.85   10.505%   $62.8221   $62.82   $62.80   $62.80  
  Purchase #3 $42.66   3.447%   $44.1305   $44.13   $44.15   $44.10  
  Purchase #4 $119.95   10.516%   $132.5639   $132.56   $132.55   $132.60  
  Purchase #5 $107.97   5.127%   $113.5056   $113.51   $113.50   $113.50  
  Purchase #6 $110.97   4.744%   $116.2344   $116.23   $116.25   $116.20  
  Purchase #7 $233.69   13.221%   $264.5862   $264.59   $264.60   $264.60  
  7 purchase totals = $847.50       $928.8179   $928.82   $928.85   $928.80