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 $241.82   8.482%   $262.3312   $262.33   $262.35   $262.30  
  Purchase #2 $42.31   3.475%   $43.7803   $43.78   $43.80   $43.80  
  Purchase #3 $214.88   9.776%   $235.8867   $235.89   $235.90   $235.90  
  Purchase #4 $181.63   7.212%   $194.7292   $194.73   $194.75   $194.70  
  Purchase #5 $241.67   10.516%   $267.084   $267.08   $267.10   $267.10  
  Purchase #6 $192.33   9.772%   $211.1245   $211.12   $211.10   $211.10  
  Purchase #7 $141.55   11.616%   $157.9924   $157.99   $158.00   $158.00  
  7 purchase totals = $1,256.19       $1,372.9283   $1,372.92   $1,373.00   $1,372.90