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	$57.30	3.393%	$59.2442	$59.24	$59.25	$59.20
Purchase #2	$153.60	13.171%	$173.8307	$173.83	$173.85	$173.80
Purchase #3	$219.98	10.709%	$243.5377	$243.54	$243.55	$243.50
Purchase #4	$225.57	7.338%	$242.1223	$242.12	$242.10	$242.10
Purchase #5	$226.30	4.433%	$236.3319	$236.33	$236.35	$236.30
Purchase #6	$57.30	4.161%	$59.6843	$59.68	$59.70	$59.70
Purchase #7	$58.78	9.272%	$64.2301	$64.23	$64.25	$64.20
7 purchase totals =	$998.83		$1,078.9812	$1,078.97	$1,079.05	$1,078.80