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 $88.71   7.332%   $95.2142   $95.21   $95.20   $95.20  
  Purchase #2 $238.45   9.172%   $260.3206   $260.32   $260.30   $260.30  
  Purchase #3 $178.48   7.505%   $191.8749   $191.87   $191.85   $191.90  
  Purchase #4 $11.84   10.514%   $13.0849   $13.08   $13.10   $13.10  
  Purchase #5 $7.69   11.620%   $8.5836   $8.58   $8.60   $8.60  
  Purchase #6 $33.61   12.704%   $37.8798   $37.88   $37.90   $37.90  
  Purchase #7 $120.68   3.198%   $124.5393   $124.54   $124.55   $124.50  
  7 purchase totals = $679.46       $731.4973   $731.48   $731.50   $731.50