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 $180.61   9.433%   $197.6469   $197.65   $197.65   $197.60  
  Purchase #2 $83.95   13.136%   $94.9777   $94.98   $95.00   $95.00  
  Purchase #3 $70.65   3.283%   $72.9694   $72.97   $72.95   $73.00  
  Purchase #4 $152.71   10.239%   $168.346   $168.35   $168.35   $168.30  
  Purchase #5 $146.36   5.782%   $154.8225   $154.82   $154.80   $154.80  
  Purchase #6 $220.46   10.160%   $242.8587   $242.86   $242.85   $242.90  
  Purchase #7 $38.98   13.153%   $44.107   $44.11   $44.10   $44.10  
  7 purchase totals = $893.72       $975.7282   $975.74   $975.70   $975.70