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	$225.27	7.802%	$242.8456	$242.85	$242.85	$242.80
Purchase #2	$20.74	5.820%	$21.9471	$21.95	$21.95	$21.90
Purchase #3	$208.31	4.261%	$217.1861	$217.19	$217.20	$217.20
Purchase #4	$146.41	7.803%	$157.8344	$157.83	$157.85	$157.80
Purchase #5	$82.56	9.483%	$90.3892	$90.39	$90.40	$90.40
Purchase #6	$144.32	10.771%	$159.8647	$159.86	$159.85	$159.90
Purchase #7	$191.42	9.201%	$209.0326	$209.03	$209.05	$209.00
7 purchase totals =	$1,019.03		$1,099.0997	$1,099.10	$1,099.15	$1,099.00