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 $209.49   11.459%   $233.4955   $233.50   $233.50   $233.50  
  Purchase #2 $244.85   9.748%   $268.718   $268.72   $268.70   $268.70  
  Purchase #3 $39.47   10.466%   $43.6009   $43.60   $43.60   $43.60  
  Purchase #4 $249.58   9.520%   $273.34   $273.34   $273.35   $273.30  
  Purchase #5 $190.36   11.259%   $211.7926   $211.79   $211.80   $211.80  
  Purchase #6 $180.73   12.847%   $203.9484   $203.95   $203.95   $203.90  
  Purchase #7 $245.99   9.510%   $269.3836   $269.38   $269.40   $269.40  
  7 purchase totals = $1,360.47       $1,504.2790   $1,504.28   $1,504.30   $1,504.20