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	$124.89	7.856%	$134.7014	$134.70	$134.70	$134.70
Purchase #2	$195.65	7.364%	$210.0577	$210.06	$210.05	$210.10
Purchase #3	$143.60	5.542%	$151.5583	$151.56	$151.55	$151.60
Purchase #4	$156.56	6.438%	$166.6393	$166.64	$166.65	$166.60
Purchase #5	$49.54	5.751%	$52.389	$52.39	$52.40	$52.40
Purchase #6	$111.72	12.111%	$125.2504	$125.25	$125.25	$125.30
Purchase #7	$97.58	13.786%	$111.0324	$111.03	$111.05	$111.00
7 purchase totals =	$879.54		$951.6285	$951.63	$951.65	$951.70