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	$152.39	13.362%	$172.7524	$172.75	$172.75	$172.80
Purchase #2	$109.75	4.314%	$114.4846	$114.48	$114.50	$114.50
Purchase #3	$245.49	9.197%	$268.0677	$268.07	$268.05	$268.10
Purchase #4	$164.41	4.769%	$172.2507	$172.25	$172.25	$172.30
Purchase #5	$160.42	3.868%	$166.625	$166.63	$166.65	$166.60
Purchase #6	$138.61	6.297%	$147.3383	$147.34	$147.35	$147.30
Purchase #7	$51.75	12.200%	$58.0635	$58.06	$58.05	$58.10
7 purchase totals =	$1,022.82		$1,099.5822	$1,099.58	$1,099.60	$1,099.70