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	$219.62	5.358%	$231.3872	$231.39	$231.40	$231.40
Purchase #2	$127.93	10.701%	$141.6198	$141.62	$141.60	$141.60
Purchase #3	$99.95	9.433%	$109.3783	$109.38	$109.40	$109.40
Purchase #4	$78.25	12.652%	$88.1502	$88.15	$88.15	$88.20
Purchase #5	$130.79	8.467%	$141.864	$141.86	$141.85	$141.90
Purchase #6	$218.60	5.370%	$230.3388	$230.34	$230.35	$230.30
Purchase #7	$188.34	11.317%	$209.6544	$209.65	$209.65	$209.70
7 purchase totals =	$1,063.48		$1,152.3927	$1,152.39	$1,152.40	$1,152.50