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	$50.26	3.324%	$51.9306	$51.93	$51.95	$51.90
Purchase #2	$90.47	10.253%	$99.7459	$99.75	$99.75	$99.70
Purchase #3	$48.89	10.145%	$53.8499	$53.85	$53.85	$53.80
Purchase #4	$92.79	6.580%	$98.8956	$98.90	$98.90	$98.90
Purchase #5	$49.55	5.167%	$52.1102	$52.11	$52.10	$52.10
Purchase #6	$37.64	3.755%	$39.0534	$39.05	$39.05	$39.10
Purchase #7	$26.82	11.152%	$29.811	$29.81	$29.80	$29.80
7 purchase totals =	$396.42		$425.3966	$425.40	$425.40	$425.30