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	$132.78	10.162%	$146.2731	$146.27	$146.25	$146.30
Purchase #2	$241.83	13.150%	$273.6306	$273.63	$273.65	$273.60
Purchase #3	$26.67	10.320%	$29.4223	$29.42	$29.40	$29.40
Purchase #4	$107.26	3.823%	$111.3605	$111.36	$111.35	$111.40
Purchase #5	$170.87	13.753%	$194.3698	$194.37	$194.35	$194.40
Purchase #6	$79.79	8.719%	$86.7469	$86.75	$86.75	$86.70
Purchase #7	$167.86	7.668%	$180.7315	$180.73	$180.75	$180.70
7 purchase totals =	$927.06		$1,022.5347	$1,022.53	$1,022.50	$1,022.50