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	$152.29	13.585%	$172.9786	$172.98	$173.00	$173.00
Purchase #2	$165.98	4.821%	$173.9819	$173.98	$174.00	$174.00
Purchase #3	$172.27	10.376%	$190.1447	$190.14	$190.15	$190.10
Purchase #4	$64.26	13.341%	$72.8329	$72.83	$72.85	$72.80
Purchase #5	$87.62	4.289%	$91.378	$91.38	$91.40	$91.40
Purchase #6	$218.82	13.328%	$247.9843	$247.98	$248.00	$248.00
Purchase #7	$174.96	11.831%	$195.6595	$195.66	$195.65	$195.70
7 purchase totals =	$1,036.20		$1,144.9599	$1,144.95	$1,145.05	$1,145.00