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	$66.55	8.594%	$72.2693	$72.27	$72.25	$72.30
Purchase #2	$49.50	3.297%	$51.132	$51.13	$51.15	$51.10
Purchase #3	$39.93	13.666%	$45.3868	$45.39	$45.40	$45.40
Purchase #4	$98.49	7.496%	$105.8728	$105.87	$105.85	$105.90
Purchase #5	$165.27	12.826%	$186.4675	$186.47	$186.45	$186.50
Purchase #6	$16.99	8.430%	$18.4223	$18.42	$18.40	$18.40
Purchase #7	$26.77	6.449%	$28.4964	$28.50	$28.50	$28.50
7 purchase totals =	$463.50		$508.0471	$508.05	$508.00	$508.10