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	$145.94	10.807%	$161.7117	$161.71	$161.70	$161.70
Purchase #2	$88.29	7.240%	$94.6822	$94.68	$94.70	$94.70
Purchase #3	$114.78	7.289%	$123.1463	$123.15	$123.15	$123.10
Purchase #4	$137.53	3.323%	$142.1001	$142.10	$142.10	$142.10
Purchase #5	$83.25	12.627%	$93.762	$93.76	$93.75	$93.80
Purchase #6	$53.73	11.178%	$59.7359	$59.74	$59.75	$59.70
Purchase #7	$22.98	5.680%	$24.2853	$24.29	$24.30	$24.30
7 purchase totals =	$646.50		$699.4235	$699.43	$699.45	$699.40