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 $91.98   3.416%   $95.122   $95.12   $95.10   $95.10  
  Purchase #2 $133.67   4.582%   $139.7948   $139.79   $139.80   $139.80  
  Purchase #3 $30.54   8.718%   $33.2025   $33.20   $33.20   $33.20  
  Purchase #4 $178.53   8.491%   $193.689   $193.69   $193.70   $193.70  
  Purchase #5 $51.96   3.809%   $53.9392   $53.94   $53.95   $53.90  
  Purchase #6 $227.69   7.252%   $244.2021   $244.20   $244.20   $244.20  
  Purchase #7 $107.86   4.650%   $112.8755   $112.88   $112.90   $112.90  
  7 purchase totals = $822.23       $872.8251   $872.82   $872.85   $872.80