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	$245.50	11.549%	$273.8528	$273.85	$273.85	$273.90
Purchase #2	$114.64	13.837%	$130.5027	$130.50	$130.50	$130.50
Purchase #3	$127.34	3.747%	$132.1114	$132.11	$132.10	$132.10
Purchase #4	$45.66	5.717%	$48.2704	$48.27	$48.25	$48.30
Purchase #5	$13.72	11.593%	$15.3106	$15.31	$15.30	$15.30
Purchase #6	$40.85	6.774%	$43.6172	$43.62	$43.60	$43.60
Purchase #7	$149.58	10.813%	$165.7541	$165.75	$165.75	$165.80
7 purchase totals =	$737.29		$809.4192	$809.41	$809.35	$809.50