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	$211.35	5.376%	$222.7122	$222.71	$222.70	$222.70
Purchase #2	$34.32	9.716%	$37.6545	$37.65	$37.65	$37.70
Purchase #3	$82.54	11.745%	$92.2343	$92.23	$92.25	$92.20
Purchase #4	$161.78	7.735%	$174.2937	$174.29	$174.30	$174.30
Purchase #5	$239.39	10.461%	$264.4326	$264.43	$264.45	$264.40
Purchase #6	$205.95	8.310%	$223.0644	$223.06	$223.05	$223.10
Purchase #7	$54.28	7.650%	$58.4324	$58.43	$58.45	$58.40
7 purchase totals =	$989.61		$1,072.8241	$1,072.80	$1,072.85	$1,072.80