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	$121.76	11.560%	$135.8355	$135.84	$135.85	$135.80
Purchase #2	$137.54	10.155%	$151.5072	$151.51	$151.50	$151.50
Purchase #3	$232.44	5.229%	$244.5943	$244.59	$244.60	$244.60
Purchase #4	$138.54	6.429%	$147.4467	$147.45	$147.45	$147.40
Purchase #5	$78.75	6.212%	$83.642	$83.64	$83.65	$83.60
Purchase #6	$50.40	4.431%	$52.6332	$52.63	$52.65	$52.60
Purchase #7	$120.79	5.602%	$127.5567	$127.56	$127.55	$127.60
7 purchase totals =	$880.22		$943.2156	$943.22	$943.25	$943.10