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 $92.27   6.272%   $98.0572   $98.06   $98.05   $98.10  
  Purchase #2 $199.30   3.663%   $206.6004   $206.60   $206.60   $206.60  
  Purchase #3 $93.98   10.874%   $104.1994   $104.20   $104.20   $104.20  
  Purchase #4 $39.95   3.412%   $41.3131   $41.31   $41.30   $41.30  
  Purchase #5 $46.96   11.271%   $52.2529   $52.25   $52.25   $52.30  
  Purchase #6 $241.32   10.774%   $267.3198   $267.32   $267.30   $267.30  
  Purchase #7 $158.61   8.446%   $172.0062   $172.01   $172.00   $172.00  
  7 purchase totals = $872.39       $941.7490   $941.75   $941.70   $941.80