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	$147.65	4.860%	$154.8258	$154.83	$154.85	$154.80
Purchase #2	$116.81	12.548%	$131.4673	$131.47	$131.45	$131.50
Purchase #3	$70.70	11.639%	$78.9288	$78.93	$78.95	$78.90
Purchase #4	$167.59	11.729%	$187.2466	$187.25	$187.25	$187.20
Purchase #5	$97.50	8.784%	$106.0644	$106.06	$106.05	$106.10
Purchase #6	$136.36	9.624%	$149.4833	$149.48	$149.50	$149.50
Purchase #7	$60.25	3.136%	$62.1394	$62.14	$62.15	$62.10
7 purchase totals =	$796.86		$870.1556	$870.16	$870.20	$870.10