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 $92.81   3.739%   $96.2802   $96.28   $96.30   $96.30  
  Purchase #2 $153.96   13.407%   $174.6014   $174.60   $174.60   $174.60  
  Purchase #3 $175.80   11.348%   $195.7498   $195.75   $195.75   $195.70  
  Purchase #4 $152.53   4.591%   $159.5327   $159.53   $159.55   $159.50  
  Purchase #5 $209.44   4.842%   $219.5811   $219.58   $219.60   $219.60  
  Purchase #6 $204.55   5.440%   $215.6775   $215.68   $215.70   $215.70  
  Purchase #7 $69.87   10.634%   $77.3   $77.30   $77.30   $77.30  
  7 purchase totals = $1,058.96       $1,138.7227   $1,138.72   $1,138.80   $1,138.70