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	$101.95	10.791%	$112.9514	$112.95	$112.95	$113.00
Purchase #2	$10.29	10.723%	$11.3934	$11.39	$11.40	$11.40
Purchase #3	$14.90	6.131%	$15.8135	$15.81	$15.80	$15.80
Purchase #4	$136.28	3.565%	$141.1384	$141.14	$141.15	$141.10
Purchase #5	$6.73	10.305%	$7.4235	$7.42	$7.40	$7.40
Purchase #6	$244.70	4.444%	$255.5745	$255.57	$255.55	$255.60
Purchase #7	$111.99	13.466%	$127.0706	$127.07	$127.05	$127.10
7 purchase totals =	$626.84		$671.3653	$671.35	$671.30	$671.40