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	$175.36	7.376%	$188.2946	$188.29	$188.30	$188.30
Purchase #2	$39.75	9.286%	$43.4412	$43.44	$43.45	$43.40
Purchase #3	$151.26	3.496%	$156.548	$156.55	$156.55	$156.50
Purchase #4	$233.84	9.688%	$256.4944	$256.49	$256.50	$256.50
Purchase #5	$101.87	9.327%	$111.3714	$111.37	$111.35	$111.40
Purchase #6	$196.58	11.562%	$219.3086	$219.31	$219.30	$219.30
Purchase #7	$207.38	13.751%	$235.8968	$235.90	$235.90	$235.90
7 purchase totals =	$1,106.04		$1,211.3550	$1,211.35	$1,211.35	$1,211.30