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	$162.93	11.196%	$181.1716	$181.17	$181.15	$181.20
Purchase #2	$65.39	10.725%	$72.4031	$72.40	$72.40	$72.40
Purchase #3	$85.57	9.447%	$93.6538	$93.65	$93.65	$93.70
Purchase #4	$90.60	9.640%	$99.3338	$99.33	$99.35	$99.30
Purchase #5	$155.26	4.170%	$161.7343	$161.73	$161.75	$161.70
Purchase #6	$19.75	3.458%	$20.433	$20.43	$20.45	$20.40
Purchase #7	$76.28	8.297%	$82.609	$82.61	$82.60	$82.60
7 purchase totals =	$655.78		$711.3386	$711.32	$711.35	$711.30