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	$187.31	12.779%	$211.2463	$211.25	$211.25	$211.20
Purchase #2	$157.73	9.537%	$172.7727	$172.77	$172.75	$172.80
Purchase #3	$89.54	10.406%	$98.8575	$98.86	$98.85	$98.90
Purchase #4	$190.60	10.788%	$211.1619	$211.16	$211.15	$211.20
Purchase #5	$71.97	4.529%	$75.2295	$75.23	$75.25	$75.20
Purchase #6	$67.30	5.400%	$70.9342	$70.93	$70.95	$70.90
Purchase #7	$218.72	11.670%	$244.2446	$244.24	$244.25	$244.20
7 purchase totals =	$983.17		$1,084.4467	$1,084.44	$1,084.45	$1,084.40