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	$233.86	9.626%	$256.3714	$256.37	$256.35	$256.40
Purchase #2	$58.92	4.551%	$61.6014	$61.60	$61.60	$61.60
Purchase #3	$131.58	9.516%	$144.1012	$144.10	$144.10	$144.10
Purchase #4	$184.27	12.583%	$207.4567	$207.46	$207.45	$207.50
Purchase #5	$26.40	3.623%	$27.3565	$27.36	$27.35	$27.40
Purchase #6	$104.82	6.367%	$111.4939	$111.49	$111.50	$111.50
Purchase #7	$206.43	8.456%	$223.8857	$223.89	$223.90	$223.90
7 purchase totals =	$946.28		$1,032.2668	$1,032.27	$1,032.25	$1,032.40