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	$85.34	10.241%	$94.0797	$94.08	$94.10	$94.10
Purchase #2	$58.44	7.525%	$62.8376	$62.84	$62.85	$62.80
Purchase #3	$150.34	4.254%	$156.7355	$156.74	$156.75	$156.70
Purchase #4	$104.91	6.297%	$111.5162	$111.52	$111.50	$111.50
Purchase #5	$124.42	4.548%	$130.0786	$130.08	$130.10	$130.10
Purchase #6	$146.59	9.852%	$161.032	$161.03	$161.05	$161.00
Purchase #7	$155.86	10.424%	$172.1068	$172.11	$172.10	$172.10
7 purchase totals =	$825.90		$888.3864	$888.40	$888.45	$888.30