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	$192.47	6.727%	$205.4175	$205.42	$205.40	$205.40
Purchase #2	$77.94	6.843%	$83.2734	$83.27	$83.25	$83.30
Purchase #3	$230.63	10.489%	$254.8208	$254.82	$254.80	$254.80
Purchase #4	$219.53	10.252%	$242.0362	$242.04	$242.05	$242.00
Purchase #5	$138.97	9.701%	$152.4515	$152.45	$152.45	$152.50
Purchase #6	$106.58	4.364%	$111.2312	$111.23	$111.25	$111.20
Purchase #7	$96.35	3.470%	$99.6933	$99.69	$99.70	$99.70
7 purchase totals =	$1,062.47		$1,148.9239	$1,148.92	$1,148.90	$1,148.90