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	$171.76	11.869%	$192.1462	$192.15	$192.15	$192.10
Purchase #2	$243.55	13.546%	$276.5413	$276.54	$276.55	$276.50
Purchase #3	$179.93	5.612%	$190.0277	$190.03	$190.05	$190.00
Purchase #4	$5.96	10.441%	$6.5823	$6.58	$6.60	$6.60
Purchase #5	$156.36	5.193%	$164.4798	$164.48	$164.50	$164.50
Purchase #6	$38.61	12.872%	$43.5799	$43.58	$43.60	$43.60
Purchase #7	$153.76	9.341%	$168.1227	$168.12	$168.10	$168.10
7 purchase totals =	$949.93		$1,041.4799	$1,041.48	$1,041.55	$1,041.40