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	$115.68	10.326%	$127.6251	$127.63	$127.65	$127.60
Purchase #2	$145.53	4.468%	$152.0323	$152.03	$152.05	$152.00
Purchase #3	$221.30	10.858%	$245.3288	$245.33	$245.35	$245.30
Purchase #4	$157.26	10.599%	$173.928	$173.93	$173.95	$173.90
Purchase #5	$147.39	10.251%	$162.4989	$162.50	$162.50	$162.50
Purchase #6	$57.95	11.490%	$64.6085	$64.61	$64.60	$64.60
Purchase #7	$18.30	4.137%	$19.0571	$19.06	$19.05	$19.10
7 purchase totals =	$863.41		$945.0787	$945.09	$945.15	$945.00