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	$157.35	10.651%	$174.1093	$174.11	$174.10	$174.10
Purchase #2	$158.38	9.807%	$173.9123	$173.91	$173.90	$173.90
Purchase #3	$154.78	12.676%	$174.3999	$174.40	$174.40	$174.40
Purchase #4	$178.40	10.253%	$196.6914	$196.69	$196.70	$196.70
Purchase #5	$87.28	13.492%	$99.0558	$99.06	$99.05	$99.10
Purchase #6	$130.82	5.861%	$138.4874	$138.49	$138.50	$138.50
Purchase #7	$93.65	11.140%	$104.0826	$104.08	$104.10	$104.10
7 purchase totals =	$960.66		$1,060.7387	$1,060.74	$1,060.75	$1,060.80