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	$91.49	12.665%	$103.0772	$103.08	$103.10	$103.10
Purchase #2	$172.68	10.329%	$190.5161	$190.52	$190.50	$190.50
Purchase #3	$95.50	5.279%	$100.5414	$100.54	$100.55	$100.50
Purchase #4	$148.52	10.431%	$164.0121	$164.01	$164.00	$164.00
Purchase #5	$221.78	13.198%	$251.0505	$251.05	$251.05	$251.10
Purchase #6	$68.78	8.813%	$74.8416	$74.84	$74.85	$74.80
Purchase #7	$158.97	10.251%	$175.266	$175.27	$175.25	$175.30
7 purchase totals =	$957.72		$1,059.3049	$1,059.31	$1,059.30	$1,059.30