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	$104.64	11.873%	$117.0639	$117.06	$117.05	$117.10
Purchase #2	$248.37	8.160%	$268.637	$268.64	$268.65	$268.60
Purchase #3	$89.73	11.336%	$99.9018	$99.90	$99.90	$99.90
Purchase #4	$11.42	10.746%	$12.6472	$12.65	$12.65	$12.60
Purchase #5	$48.97	13.530%	$55.5956	$55.60	$55.60	$55.60
Purchase #6	$247.91	7.260%	$265.9083	$265.91	$265.90	$265.90
Purchase #7	$207.52	13.685%	$235.9191	$235.92	$235.90	$235.90
7 purchase totals =	$958.56		$1,055.6729	$1,055.68	$1,055.65	$1,055.60