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	$146.48	5.117%	$153.9754	$153.98	$154.00	$154.00
Purchase #2	$99.31	5.784%	$105.0541	$105.05	$105.05	$105.10
Purchase #3	$153.79	5.778%	$162.676	$162.68	$162.70	$162.70
Purchase #4	$150.66	3.689%	$156.2178	$156.22	$156.20	$156.20
Purchase #5	$59.42	12.160%	$66.6455	$66.65	$66.65	$66.60
Purchase #6	$160.48	12.738%	$180.9219	$180.92	$180.90	$180.90
Purchase #7	$195.71	10.267%	$215.8035	$215.80	$215.80	$215.80
7 purchase totals =	$965.85		$1,041.2942	$1,041.30	$1,041.30	$1,041.30