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 $240.55   10.174%   $265.0236   $265.02   $265.00   $265.00  
  Purchase #2 $211.82   10.465%   $233.987   $233.99   $234.00   $234.00  
  Purchase #3 $10.86   6.567%   $11.5732   $11.57   $11.55   $11.60  
  Purchase #4 $55.57   10.543%   $61.4287   $61.43   $61.45   $61.40  
  Purchase #5 $226.65   7.845%   $244.4307   $244.43   $244.45   $244.40  
  Purchase #6 $223.87   9.129%   $244.3071   $244.31   $244.30   $244.30  
  Purchase #7 $126.96   5.777%   $134.2945   $134.29   $134.30   $134.30  
  7 purchase totals = $1,096.28       $1,195.0448   $1,195.04   $1,195.05   $1,195.00