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	$213.45	10.373%	$235.5912	$235.59	$235.60	$235.60
Purchase #2	$88.68	11.513%	$98.8897	$98.89	$98.90	$98.90
Purchase #3	$172.71	4.173%	$179.9172	$179.92	$179.90	$179.90
Purchase #4	$164.75	6.616%	$175.6499	$175.65	$175.65	$175.60
Purchase #5	$149.53	13.178%	$169.2351	$169.24	$169.25	$169.20
Purchase #6	$155.86	10.640%	$172.4435	$172.44	$172.45	$172.40
Purchase #7	$129.88	9.374%	$142.055	$142.06	$142.05	$142.10
7 purchase totals =	$1,074.86		$1,173.7816	$1,173.79	$1,173.80	$1,173.70