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	$75.92	9.399%	$83.0557	$83.06	$83.05	$83.10
Purchase #2	$147.31	13.137%	$166.6621	$166.66	$166.65	$166.70
Purchase #3	$174.68	6.263%	$185.6202	$185.62	$185.60	$185.60
Purchase #4	$37.63	6.130%	$39.9367	$39.94	$39.95	$39.90
Purchase #5	$230.53	8.373%	$249.8323	$249.83	$249.85	$249.80
Purchase #6	$117.54	7.104%	$125.89	$125.89	$125.90	$125.90
Purchase #7	$145.42	7.701%	$156.6188	$156.62	$156.60	$156.60
7 purchase totals =	$929.03		$1,007.6158	$1,007.62	$1,007.60	$1,007.60