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	$57.39	8.574%	$62.3106	$62.31	$62.30	$62.30
Purchase #2	$244.29	11.350%	$272.0169	$272.02	$272.00	$272.00
Purchase #3	$113.68	7.687%	$122.4186	$122.42	$122.40	$122.40
Purchase #4	$160.74	7.200%	$172.3133	$172.31	$172.30	$172.30
Purchase #5	$141.72	6.126%	$150.4018	$150.40	$150.40	$150.40
Purchase #6	$29.61	11.232%	$32.9358	$32.94	$32.95	$32.90
Purchase #7	$37.98	13.824%	$43.2304	$43.23	$43.25	$43.20
7 purchase totals =	$785.41		$855.6274	$855.63	$855.60	$855.50