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	$88.56	7.365%	$95.0824	$95.08	$95.10	$95.10
Purchase #2	$31.50	9.164%	$34.3867	$34.39	$34.40	$34.40
Purchase #3	$79.94	12.266%	$89.7454	$89.75	$89.75	$89.70
Purchase #4	$87.68	10.563%	$96.9416	$96.94	$96.95	$96.90
Purchase #5	$11.35	11.846%	$12.6945	$12.69	$12.70	$12.70
Purchase #6	$28.37	10.228%	$31.2717	$31.27	$31.25	$31.30
Purchase #7	$122.42	13.262%	$138.6553	$138.66	$138.65	$138.70
7 purchase totals =	$449.82		$498.7776	$498.78	$498.80	$498.80