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 $92.34   3.682%   $95.74   $95.74   $95.75   $95.70  
  Purchase #2 $55.77   4.354%   $58.1982   $58.20   $58.20   $58.20  
  Purchase #3 $98.57   7.425%   $105.8888   $105.89   $105.90   $105.90  
  Purchase #4 $93.35   13.555%   $106.0036   $106.00   $106.00   $106.00  
  Purchase #5 $45.99   4.404%   $48.0154   $48.02   $48.00   $48.00  
  Purchase #6 $71.94   5.368%   $75.8017   $75.80   $75.80   $75.80  
  Purchase #7 $223.28   12.686%   $251.6053   $251.61   $251.60   $251.60  
  7 purchase totals = $681.24       $741.2530   $741.26   $741.25   $741.20