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	$171.29	3.140%	$176.6685	$176.67	$176.65	$176.70
Purchase #2	$115.90	11.375%	$129.0836	$129.08	$129.10	$129.10
Purchase #3	$247.71	6.731%	$264.3834	$264.38	$264.40	$264.40
Purchase #4	$120.27	7.107%	$128.8176	$128.82	$128.80	$128.80
Purchase #5	$127.58	13.407%	$144.6847	$144.68	$144.70	$144.70
Purchase #6	$87.95	13.417%	$99.7503	$99.75	$99.75	$99.80
Purchase #7	$235.43	7.629%	$253.391	$253.39	$253.40	$253.40
7 purchase totals =	$1,106.13		$1,196.7791	$1,196.77	$1,196.80	$1,196.90