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	$169.34	8.558%	$183.8321	$183.83	$183.85	$183.80
Purchase #2	$116.35	10.763%	$128.8728	$128.87	$128.85	$128.90
Purchase #3	$45.32	3.148%	$46.7467	$46.75	$46.75	$46.70
Purchase #4	$161.48	8.523%	$175.2429	$175.24	$175.25	$175.20
Purchase #5	$94.29	5.262%	$99.2515	$99.25	$99.25	$99.30
Purchase #6	$111.37	4.352%	$116.2168	$116.22	$116.20	$116.20
Purchase #7	$158.42	10.736%	$175.428	$175.43	$175.45	$175.40
7 purchase totals =	$856.57		$925.5908	$925.59	$925.60	$925.50