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 $92.71   3.512%   $95.966   $95.97   $95.95   $96.00  
  Purchase #2 $69.46   6.549%   $74.0089   $74.01   $74.00   $74.00  
  Purchase #3 $219.99   9.736%   $241.4082   $241.41   $241.40   $241.40  
  Purchase #4 $25.73   6.765%   $27.4706   $27.47   $27.45   $27.50  
  Purchase #5 $40.82   10.375%   $45.0551   $45.06   $45.05   $45.10  
  Purchase #6 $77.36   4.552%   $80.8814   $80.88   $80.90   $80.90  
  Purchase #7 $165.84   10.226%   $182.7988   $182.80   $182.80   $182.80  
  7 purchase totals = $691.91       $747.5890   $747.60   $747.55   $747.70