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 $195.60   3.402%   $202.2543   $202.25   $202.25   $202.30  
  Purchase #2 $57.75   4.279%   $60.2211   $60.22   $60.20   $60.20  
  Purchase #3 $10.40   4.433%   $10.861   $10.86   $10.85   $10.90  
  Purchase #4 $235.36   12.385%   $264.5093   $264.51   $264.50   $264.50  
  Purchase #5 $157.92   6.649%   $168.4201   $168.42   $168.40   $168.40  
  Purchase #6 $233.40   8.133%   $252.3824   $252.38   $252.40   $252.40  
  Purchase #7 $85.86   9.325%   $93.8664   $93.87   $93.85   $93.90  
  7 purchase totals = $976.29       $1,052.5146   $1,052.51   $1,052.45   $1,052.60