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 $222.75   9.802%   $244.584   $244.58   $244.60   $244.60  
  Purchase #2 $199.66   3.812%   $207.271   $207.27   $207.25   $207.30  
  Purchase #3 $66.46   12.622%   $74.8486   $74.85   $74.85   $74.80  
  Purchase #4 $12.29   10.115%   $13.5331   $13.53   $13.55   $13.50  
  Purchase #5 $82.31   3.113%   $84.8723   $84.87   $84.85   $84.90  
  Purchase #6 $241.36   10.754%   $267.3159   $267.32   $267.30   $267.30  
  Purchase #7 $152.90   11.658%   $170.7251   $170.73   $170.75   $170.70  
  7 purchase totals = $977.73       $1,063.1500   $1,063.15   $1,063.15   $1,063.10