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	$210.35	6.523%	$224.0711	$224.07	$224.05	$224.10
Purchase #2	$83.66	7.383%	$89.8366	$89.84	$89.85	$89.80
Purchase #3	$178.55	7.859%	$192.5822	$192.58	$192.60	$192.60
Purchase #4	$240.86	13.422%	$273.1882	$273.19	$273.20	$273.20
Purchase #5	$50.48	5.213%	$53.1115	$53.11	$53.10	$53.10
Purchase #6	$83.53	7.126%	$89.4823	$89.48	$89.50	$89.50
Purchase #7	$20.94	7.158%	$22.4389	$22.44	$22.45	$22.40
7 purchase totals =	$868.37		$944.7108	$944.71	$944.75	$944.70