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 $119.33   10.360%   $131.6926   $131.69   $131.70   $131.70  
  Purchase #2 $208.75   10.265%   $230.1782   $230.18   $230.20   $230.20  
  Purchase #3 $26.37   12.201%   $29.5874   $29.59   $29.60   $29.60  
  Purchase #4 $55.31   11.363%   $61.5949   $61.59   $61.60   $61.60  
  Purchase #5 $194.62   9.810%   $213.7122   $213.71   $213.70   $213.70  
  Purchase #6 $43.64   11.703%   $48.7472   $48.75   $48.75   $48.70  
  Purchase #7 $15.62   7.376%   $16.7721   $16.77   $16.75   $16.80  
  7 purchase totals = $663.64       $732.2846   $732.28   $732.30   $732.30