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	$83.92	13.732%	$95.4439	$95.44	$95.45	$95.40
Purchase #2	$38.52	8.583%	$41.8262	$41.83	$41.85	$41.80
Purchase #3	$91.98	7.774%	$99.1305	$99.13	$99.15	$99.10
Purchase #4	$39.68	4.401%	$41.4263	$41.43	$41.45	$41.40
Purchase #5	$22.32	9.294%	$24.3944	$24.39	$24.40	$24.40
Purchase #6	$19.39	4.138%	$20.1924	$20.19	$20.20	$20.20
Purchase #7	$161.54	13.322%	$183.0604	$183.06	$183.05	$183.10
7 purchase totals =	$457.35		$505.4741	$505.47	$505.55	$505.40