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	$168.71	12.784%	$190.2779	$190.28	$190.30	$190.30
Purchase #2	$236.91	4.436%	$247.4193	$247.42	$247.40	$247.40
Purchase #3	$90.38	5.191%	$95.0716	$95.07	$95.05	$95.10
Purchase #4	$198.62	11.428%	$221.3183	$221.32	$221.30	$221.30
Purchase #5	$118.25	4.349%	$123.3927	$123.39	$123.40	$123.40
Purchase #6	$110.67	10.491%	$122.2804	$122.28	$122.30	$122.30
Purchase #7	$137.47	10.783%	$152.2934	$152.29	$152.30	$152.30
7 purchase totals =	$1,061.01		$1,152.0536	$1,152.05	$1,152.05	$1,152.10