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	$86.83	13.627%	$98.6623	$98.66	$98.65	$98.70
Purchase #2	$152.62	9.821%	$167.6088	$167.61	$167.60	$167.60
Purchase #3	$242.92	6.801%	$259.441	$259.44	$259.45	$259.40
Purchase #4	$47.72	6.154%	$50.6567	$50.66	$50.65	$50.70
Purchase #5	$9.50	12.790%	$10.7151	$10.72	$10.70	$10.70
Purchase #6	$101.88	10.375%	$112.4501	$112.45	$112.45	$112.50
Purchase #7	$100.50	11.413%	$111.9701	$111.97	$111.95	$112.00
7 purchase totals =	$741.97		$811.5041	$811.51	$811.45	$811.60