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 $44.38   6.465%   $47.2492   $47.25   $47.25   $47.20  
  Purchase #2 $223.42   4.412%   $233.2773   $233.28   $233.30   $233.30  
  Purchase #3 $195.87   11.790%   $218.9631   $218.96   $218.95   $219.00  
  Purchase #4 $241.64   9.475%   $264.5354   $264.54   $264.55   $264.50  
  Purchase #5 $204.63   9.424%   $223.9143   $223.91   $223.90   $223.90  
  Purchase #6 $87.63   6.326%   $93.1735   $93.17   $93.15   $93.20  
  Purchase #7 $217.52   3.776%   $225.7336   $225.73   $225.75   $225.70  
  7 purchase totals = $1,215.09       $1,306.8464   $1,306.84   $1,306.85   $1,306.80