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	$94.94	9.636%	$104.0884	$104.09	$104.10	$104.10
Purchase #2	$22.35	9.478%	$24.4683	$24.47	$24.45	$24.50
Purchase #3	$98.84	5.745%	$104.5184	$104.52	$104.50	$104.50
Purchase #4	$70.81	4.218%	$73.7968	$73.80	$73.80	$73.80
Purchase #5	$240.76	5.250%	$253.3999	$253.40	$253.40	$253.40
Purchase #6	$118.43	11.258%	$131.7628	$131.76	$131.75	$131.80
Purchase #7	$56.30	8.450%	$61.0574	$61.06	$61.05	$61.10
7 purchase totals =	$702.43		$753.0920	$753.10	$753.05	$753.20