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	$48.64	10.786%	$53.8863	$53.89	$53.90	$53.90
Purchase #2	$220.69	9.731%	$242.1653	$242.17	$242.15	$242.20
Purchase #3	$223.27	12.783%	$251.8106	$251.81	$251.80	$251.80
Purchase #4	$235.42	6.261%	$250.1596	$250.16	$250.15	$250.20
Purchase #5	$88.59	8.454%	$96.0794	$96.08	$96.10	$96.10
Purchase #6	$177.39	12.339%	$199.2782	$199.28	$199.30	$199.30
Purchase #7	$60.69	7.163%	$65.0372	$65.04	$65.05	$65.00
7 purchase totals =	$1,054.69		$1,158.4166	$1,158.43	$1,158.45	$1,158.50