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 $244.30   7.630%   $262.9401   $262.94   $262.95   $262.90  
  Purchase #2 $159.25   13.236%   $180.3283   $180.33   $180.35   $180.30  
  Purchase #3 $111.68   10.180%   $123.049   $123.05   $123.05   $123.00  
  Purchase #4 $142.97   6.747%   $152.6162   $152.62   $152.60   $152.60  
  Purchase #5 $99.89   7.166%   $107.0481   $107.05   $107.05   $107.00  
  Purchase #6 $217.60   8.593%   $236.2984   $236.30   $236.30   $236.30  
  Purchase #7 $104.42   12.104%   $117.059   $117.06   $117.05   $117.10  
  7 purchase totals = $1,080.11       $1,179.3391   $1,179.35   $1,179.35   $1,179.20