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	$220.51	3.210%	$227.5884	$227.59	$227.60	$227.60
Purchase #2	$162.36	11.792%	$181.5055	$181.51	$181.50	$181.50
Purchase #3	$68.29	4.321%	$71.2408	$71.24	$71.25	$71.20
Purchase #4	$14.68	13.440%	$16.653	$16.65	$16.65	$16.70
Purchase #5	$30.25	9.275%	$33.0557	$33.06	$33.05	$33.10
Purchase #6	$178.78	9.858%	$196.4041	$196.40	$196.40	$196.40
Purchase #7	$14.69	7.630%	$15.8108	$15.81	$15.80	$15.80
7 purchase totals =	$689.56		$742.2583	$742.26	$742.25	$742.30