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 $110.80   13.674%   $125.9508   $125.95   $125.95   $126.00  
  Purchase #2 $53.83   6.764%   $57.4711   $57.47   $57.45   $57.50  
  Purchase #3 $189.65   6.431%   $201.8464   $201.85   $201.85   $201.80  
  Purchase #4 $14.81   9.853%   $16.2692   $16.27   $16.25   $16.30  
  Purchase #5 $70.51   9.870%   $77.4693   $77.47   $77.45   $77.50  
  Purchase #6 $233.57   11.490%   $260.4072   $260.41   $260.40   $260.40  
  Purchase #7 $92.93   3.315%   $96.0106   $96.01   $96.00   $96.00  
  7 purchase totals = $766.10       $835.4246   $835.43   $835.35   $835.50