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	$87.38	4.307%	$91.1435	$91.14	$91.15	$91.10
Purchase #2	$26.99	6.487%	$28.7408	$28.74	$28.75	$28.70
Purchase #3	$183.78	8.813%	$199.9765	$199.98	$200.00	$200.00
Purchase #4	$214.40	13.416%	$243.1639	$243.16	$243.15	$243.20
Purchase #5	$63.63	13.645%	$72.3123	$72.31	$72.30	$72.30
Purchase #6	$99.78	3.303%	$103.0757	$103.08	$103.10	$103.10
Purchase #7	$34.26	10.501%	$37.8576	$37.86	$37.85	$37.90
7 purchase totals =	$710.22		$776.2703	$776.27	$776.30	$776.30