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	$144.85	3.337%	$149.6836	$149.68	$149.70	$149.70
Purchase #2	$187.66	7.437%	$201.6163	$201.62	$201.60	$201.60
Purchase #3	$219.39	11.723%	$245.1091	$245.11	$245.10	$245.10
Purchase #4	$50.70	5.169%	$53.3207	$53.32	$53.30	$53.30
Purchase #5	$82.59	8.769%	$89.8323	$89.83	$89.85	$89.80
Purchase #6	$190.83	10.840%	$211.516	$211.52	$211.50	$211.50
Purchase #7	$141.64	4.850%	$148.5095	$148.51	$148.50	$148.50
7 purchase totals =	$1,017.66		$1,099.5875	$1,099.59	$1,099.55	$1,099.50