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 $90.83   5.326%   $95.6676   $95.67   $95.65   $95.70  
  Purchase #2 $100.98   12.442%   $113.5439   $113.54   $113.55   $113.50  
  Purchase #3 $193.77   10.149%   $213.4357   $213.44   $213.45   $213.40  
  Purchase #4 $233.27   4.790%   $244.4436   $244.44   $244.45   $244.40  
  Purchase #5 $40.59   11.741%   $45.3557   $45.36   $45.35   $45.40  
  Purchase #6 $184.40   11.151%   $204.9624   $204.96   $204.95   $205.00  
  Purchase #7 $245.77   12.578%   $276.683   $276.68   $276.70   $276.70  
  7 purchase totals = $1,089.61       $1,194.0919   $1,194.09   $1,194.10   $1,194.10