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	$146.59	5.408%	$154.5176	$154.52	$154.50	$154.50
Purchase #2	$69.48	4.521%	$72.6212	$72.62	$72.60	$72.60
Purchase #3	$123.78	6.433%	$131.7428	$131.74	$131.75	$131.70
Purchase #4	$240.70	4.157%	$250.7059	$250.71	$250.70	$250.70
Purchase #5	$217.43	9.856%	$238.8599	$238.86	$238.85	$238.90
Purchase #6	$116.43	3.850%	$120.9126	$120.91	$120.90	$120.90
Purchase #7	$232.34	9.449%	$254.2938	$254.29	$254.30	$254.30
7 purchase totals =	$1,146.75		$1,223.6538	$1,223.65	$1,223.60	$1,223.60