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 $213.34   9.558%   $233.731   $233.73   $233.75   $233.70  
  Purchase #2 $90.56   6.638%   $96.5714   $96.57   $96.55   $96.60  
  Purchase #3 $43.75   8.800%   $47.6   $47.60   $47.60   $47.60  
  Purchase #4 $35.72   9.699%   $39.1845   $39.18   $39.20   $39.20  
  Purchase #5 $120.89   11.644%   $134.9664   $134.97   $134.95   $135.00  
  Purchase #6 $173.96   5.744%   $183.9523   $183.95   $183.95   $184.00  
  Purchase #7 $204.55   7.606%   $220.1081   $220.11   $220.10   $220.10  
  7 purchase totals = $882.77       $956.1137   $956.11   $956.10   $956.20