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	$41.66	3.823%	$43.2527	$43.25	$43.25	$43.30
Purchase #2	$200.40	13.107%	$226.6664	$226.67	$226.65	$226.70
Purchase #3	$94.47	6.746%	$100.8429	$100.84	$100.85	$100.80
Purchase #4	$24.92	4.225%	$25.9729	$25.97	$25.95	$26.00
Purchase #5	$67.25	10.277%	$74.1613	$74.16	$74.15	$74.20
Purchase #6	$96.40	13.353%	$109.2723	$109.27	$109.25	$109.30
Purchase #7	$111.43	10.805%	$123.47	$123.47	$123.45	$123.50
7 purchase totals =	$636.53		$703.6385	$703.63	$703.55	$703.80