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	$166.71	5.310%	$175.5623	$175.56	$175.55	$175.60
Purchase #2	$234.97	12.141%	$263.4977	$263.50	$263.50	$263.50
Purchase #3	$235.36	13.218%	$266.4699	$266.47	$266.45	$266.50
Purchase #4	$69.64	4.360%	$72.6763	$72.68	$72.70	$72.70
Purchase #5	$115.36	10.502%	$127.4751	$127.48	$127.50	$127.50
Purchase #6	$36.48	11.650%	$40.7299	$40.73	$40.75	$40.70
Purchase #7	$226.46	13.341%	$256.672	$256.67	$256.65	$256.70
7 purchase totals =	$1,084.98		$1,203.0832	$1,203.09	$1,203.10	$1,203.20