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	$212.52	5.440%	$224.0811	$224.08	$224.10	$224.10
Purchase #2	$95.73	4.196%	$99.7468	$99.75	$99.75	$99.70
Purchase #3	$234.55	12.805%	$264.5841	$264.58	$264.60	$264.60
Purchase #4	$12.92	4.506%	$13.5022	$13.50	$13.50	$13.50
Purchase #5	$250.88	6.786%	$267.9047	$267.90	$267.90	$267.90
Purchase #6	$127.43	4.202%	$132.7846	$132.78	$132.80	$132.80
Purchase #7	$149.89	13.141%	$169.587	$169.59	$169.60	$169.60
7 purchase totals =	$1,083.92		$1,172.1905	$1,172.18	$1,172.25	$1,172.20