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 $64.85   12.495%   $72.953   $72.95   $72.95   $73.00  
  Purchase #2 $194.40   9.441%   $212.7533   $212.75   $212.75   $212.80  
  Purchase #3 $144.83   11.677%   $161.7418   $161.74   $161.75   $161.70  
  Purchase #4 $116.40   10.215%   $128.2903   $128.29   $128.30   $128.30  
  Purchase #5 $108.64   12.222%   $121.918   $121.92   $121.90   $121.90  
  Purchase #6 $235.40   4.599%   $246.226   $246.23   $246.25   $246.20  
  Purchase #7 $158.27   10.114%   $174.2774   $174.28   $174.30   $174.30  
  7 purchase totals = $1,022.79       $1,118.1598   $1,118.16   $1,118.20   $1,118.20