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	$60.80	7.374%	$65.2834	$65.28	$65.30	$65.30
Purchase #2	$83.84	6.631%	$89.3994	$89.40	$89.40	$89.40
Purchase #3	$92.32	10.265%	$101.7966	$101.80	$101.80	$101.80
Purchase #4	$40.51	11.595%	$45.2071	$45.21	$45.20	$45.20
Purchase #5	$209.33	9.219%	$228.6281	$228.63	$228.65	$228.60
Purchase #6	$32.97	13.184%	$37.3168	$37.32	$37.30	$37.30
Purchase #7	$67.40	10.333%	$74.3644	$74.36	$74.35	$74.40
7 purchase totals =	$587.17		$641.9958	$642.00	$642.00	$642.00