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	$157.69	10.111%	$173.634	$173.63	$173.65	$173.60
Purchase #2	$122.83	11.482%	$136.9333	$136.93	$136.95	$136.90
Purchase #3	$55.83	8.391%	$60.5147	$60.51	$60.50	$60.50
Purchase #4	$84.56	10.445%	$93.3923	$93.39	$93.40	$93.40
Purchase #5	$91.35	8.682%	$99.281	$99.28	$99.30	$99.30
Purchase #6	$64.58	4.236%	$67.3156	$67.32	$67.30	$67.30
Purchase #7	$233.47	9.244%	$255.052	$255.05	$255.05	$255.10
7 purchase totals =	$810.31		$886.1229	$886.11	$886.15	$886.10