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	$159.74	7.388%	$171.5416	$171.54	$171.55	$171.50
Purchase #2	$159.53	7.123%	$170.8933	$170.89	$170.90	$170.90
Purchase #3	$50.31	7.176%	$53.9202	$53.92	$53.90	$53.90
Purchase #4	$154.83	7.532%	$166.4918	$166.49	$166.50	$166.50
Purchase #5	$181.65	13.740%	$206.6087	$206.61	$206.60	$206.60
Purchase #6	$107.27	9.196%	$117.1345	$117.13	$117.15	$117.10
Purchase #7	$56.84	5.178%	$59.7832	$59.78	$59.80	$59.80
7 purchase totals =	$870.17		$946.3733	$946.36	$946.40	$946.30