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	$104.89	6.368%	$111.5694	$111.57	$111.55	$111.60
Purchase #2	$9.38	13.135%	$10.6121	$10.61	$10.60	$10.60
Purchase #3	$211.71	8.321%	$229.3264	$229.33	$229.35	$229.30
Purchase #4	$155.33	7.180%	$166.4827	$166.48	$166.50	$166.50
Purchase #5	$127.35	3.807%	$132.1982	$132.20	$132.20	$132.20
Purchase #6	$152.92	11.826%	$171.0043	$171.00	$171.00	$171.00
Purchase #7	$132.51	10.327%	$146.1943	$146.19	$146.20	$146.20
7 purchase totals =	$894.09		$967.3874	$967.38	$967.40	$967.40