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	$230.37	10.620%	$254.8353	$254.84	$254.85	$254.80
Purchase #2	$228.70	10.681%	$253.1274	$253.13	$253.15	$253.10
Purchase #3	$66.87	7.636%	$71.9762	$71.98	$72.00	$72.00
Purchase #4	$147.58	11.547%	$164.6211	$164.62	$164.60	$164.60
Purchase #5	$79.93	13.109%	$90.408	$90.41	$90.40	$90.40
Purchase #6	$244.75	4.283%	$255.2326	$255.23	$255.25	$255.20
Purchase #7	$73.80	13.319%	$83.6294	$83.63	$83.65	$83.60
7 purchase totals =	$1,072.00		$1,173.8300	$1,173.84	$1,173.90	$1,173.70