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	$87.95	11.582%	$98.1364	$98.14	$98.15	$98.10
Purchase #2	$86.49	4.822%	$90.6605	$90.66	$90.65	$90.70
Purchase #3	$72.47	7.851%	$78.1596	$78.16	$78.15	$78.20
Purchase #4	$108.92	10.683%	$120.5559	$120.56	$120.55	$120.60
Purchase #5	$22.91	10.619%	$25.3428	$25.34	$25.35	$25.30
Purchase #6	$145.87	3.717%	$151.292	$151.29	$151.30	$151.30
Purchase #7	$56.43	8.275%	$61.0996	$61.10	$61.10	$61.10
7 purchase totals =	$581.04		$625.2468	$625.25	$625.25	$625.30