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	$205.71	3.261%	$212.4182	$212.42	$212.40	$212.40
Purchase #2	$217.83	11.812%	$243.5601	$243.56	$243.55	$243.60
Purchase #3	$117.32	10.218%	$129.3078	$129.31	$129.30	$129.30
Purchase #4	$46.69	11.130%	$51.8866	$51.89	$51.90	$51.90
Purchase #5	$175.65	8.247%	$190.1359	$190.14	$190.15	$190.10
Purchase #6	$218.90	11.217%	$243.454	$243.45	$243.45	$243.50
Purchase #7	$164.53	9.167%	$179.6125	$179.61	$179.60	$179.60
7 purchase totals =	$1,146.63		$1,250.3751	$1,250.38	$1,250.35	$1,250.40