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	$98.68	10.109%	$108.6556	$108.66	$108.65	$108.70
Purchase #2	$206.70	10.381%	$228.1575	$228.16	$228.15	$228.20
Purchase #3	$205.30	10.693%	$227.2527	$227.25	$227.25	$227.30
Purchase #4	$214.62	4.268%	$223.78	$223.78	$223.80	$223.80
Purchase #5	$250.61	5.271%	$263.8197	$263.82	$263.80	$263.80
Purchase #6	$59.39	9.283%	$64.9032	$64.90	$64.90	$64.90
Purchase #7	$32.73	13.758%	$37.233	$37.23	$37.25	$37.20
7 purchase totals =	$1,068.03		$1,153.8017	$1,153.80	$1,153.80	$1,153.90