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 $115.53   9.534%   $126.5446   $126.54   $126.55   $126.50  
  Purchase #2 $172.65   11.188%   $191.9661   $191.97   $191.95   $192.00  
  Purchase #3 $48.62   7.113%   $52.0783   $52.08   $52.10   $52.10  
  Purchase #4 $96.71   13.344%   $109.615   $109.62   $109.60   $109.60  
  Purchase #5 $209.48   11.224%   $232.992   $232.99   $233.00   $233.00  
  Purchase #6 $237.33   3.308%   $245.1809   $245.18   $245.20   $245.20  
  Purchase #7 $60.75   9.262%   $66.3767   $66.38   $66.40   $66.40  
  7 purchase totals = $941.07       $1,024.7536   $1,024.76   $1,024.80   $1,024.80