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	$152.78	4.285%	$159.3266	$159.33	$159.35	$159.30
Purchase #2	$96.41	3.107%	$99.4055	$99.41	$99.40	$99.40
Purchase #3	$169.37	13.537%	$192.2976	$192.30	$192.30	$192.30
Purchase #4	$194.51	12.380%	$218.5903	$218.59	$218.60	$218.60
Purchase #5	$248.78	10.836%	$275.7378	$275.74	$275.75	$275.70
Purchase #6	$139.72	4.771%	$146.386	$146.39	$146.40	$146.40
Purchase #7	$130.87	6.867%	$139.8568	$139.86	$139.85	$139.90
7 purchase totals =	$1,132.44		$1,231.6006	$1,231.62	$1,231.65	$1,231.60