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	$118.77	10.788%	$131.5829	$131.58	$131.60	$131.60
Purchase #2	$131.86	10.507%	$145.7145	$145.71	$145.70	$145.70
Purchase #3	$18.66	4.160%	$19.4363	$19.44	$19.45	$19.40
Purchase #4	$99.50	11.636%	$111.0778	$111.08	$111.10	$111.10
Purchase #5	$222.93	9.562%	$244.2466	$244.25	$244.25	$244.20
Purchase #6	$125.64	10.798%	$139.2066	$139.21	$139.20	$139.20
Purchase #7	$111.92	9.783%	$122.8691	$122.87	$122.85	$122.90
7 purchase totals =	$829.28		$914.1338	$914.14	$914.15	$914.10