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	$41.63	11.754%	$46.5232	$46.52	$46.50	$46.50
Purchase #2	$34.65	7.694%	$37.316	$37.32	$37.30	$37.30
Purchase #3	$242.72	8.691%	$263.8148	$263.81	$263.80	$263.80
Purchase #4	$77.71	6.673%	$82.8956	$82.90	$82.90	$82.90
Purchase #5	$233.61	11.640%	$260.8022	$260.80	$260.80	$260.80
Purchase #6	$230.93	5.133%	$242.7836	$242.78	$242.80	$242.80
Purchase #7	$29.87	11.689%	$33.3615	$33.36	$33.35	$33.40
7 purchase totals =	$891.12		$967.4969	$967.49	$967.45	$967.50