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	$161.36	7.173%	$172.9344	$172.93	$172.95	$172.90
Purchase #2	$200.81	9.333%	$219.5516	$219.55	$219.55	$219.60
Purchase #3	$111.49	3.180%	$115.0354	$115.04	$115.05	$115.00
Purchase #4	$123.61	11.232%	$137.4939	$137.49	$137.50	$137.50
Purchase #5	$26.48	6.830%	$28.2886	$28.29	$28.30	$28.30
Purchase #6	$79.97	13.132%	$90.4717	$90.47	$90.45	$90.50
Purchase #7	$40.91	4.743%	$42.8504	$42.85	$42.85	$42.90
7 purchase totals =	$744.63		$806.6260	$806.62	$806.65	$806.70