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	$41.74	4.222%	$43.5023	$43.50	$43.50	$43.50
Purchase #2	$20.27	3.176%	$20.9138	$20.91	$20.90	$20.90
Purchase #3	$31.85	8.603%	$34.5901	$34.59	$34.60	$34.60
Purchase #4	$78.53	5.522%	$82.8664	$82.87	$82.85	$82.90
Purchase #5	$31.54	13.490%	$35.7947	$35.79	$35.80	$35.80
Purchase #6	$17.78	11.471%	$19.8195	$19.82	$19.80	$19.80
Purchase #7	$194.28	7.690%	$209.2201	$209.22	$209.20	$209.20
7 purchase totals =	$415.99		$446.7069	$446.70	$446.65	$446.70