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	$111.36	10.123%	$122.633	$122.63	$122.65	$122.60
Purchase #2	$121.96	7.722%	$131.3778	$131.38	$131.40	$131.40
Purchase #3	$151.51	8.286%	$164.0641	$164.06	$164.05	$164.10
Purchase #4	$90.46	6.807%	$96.6176	$96.62	$96.60	$96.60
Purchase #5	$43.30	9.608%	$47.4603	$47.46	$47.45	$47.50
Purchase #6	$69.59	6.145%	$73.8663	$73.87	$73.85	$73.90
Purchase #7	$160.55	3.335%	$165.9043	$165.90	$165.90	$165.90
7 purchase totals =	$748.73		$801.9234	$801.92	$801.90	$802.00