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	$96.35	13.288%	$109.153	$109.15	$109.15	$109.20
Purchase #2	$32.72	11.741%	$36.5617	$36.56	$36.55	$36.60
Purchase #3	$210.93	5.672%	$222.8939	$222.89	$222.90	$222.90
Purchase #4	$226.61	11.381%	$252.4005	$252.40	$252.40	$252.40
Purchase #5	$174.76	6.261%	$185.7017	$185.70	$185.70	$185.70
Purchase #6	$51.70	4.326%	$53.9365	$53.94	$53.95	$53.90
Purchase #7	$95.63	3.624%	$99.0956	$99.10	$99.10	$99.10
7 purchase totals =	$888.70		$959.7429	$959.74	$959.75	$959.80