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 $211.37   3.445%   $218.6517   $218.65   $218.65   $218.70  
  Purchase #2 $225.36   12.365%   $253.2258   $253.23   $253.25   $253.20  
  Purchase #3 $243.70   11.175%   $270.9335   $270.93   $270.95   $270.90  
  Purchase #4 $36.78   11.490%   $41.006   $41.01   $41.00   $41.00  
  Purchase #5 $204.54   5.847%   $216.4995   $216.50   $216.50   $216.50  
  Purchase #6 $41.56   4.234%   $43.3197   $43.32   $43.30   $43.30  
  Purchase #7 $233.69   4.577%   $244.386   $244.39   $244.40   $244.40  
  7 purchase totals = $1,197.00       $1,288.0222   $1,288.03   $1,288.05   $1,288.00