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	$106.58	8.721%	$115.8748	$115.87	$115.85	$115.90
Purchase #2	$96.46	9.523%	$105.6459	$105.65	$105.65	$105.60
Purchase #3	$173.59	9.475%	$190.0377	$190.04	$190.05	$190.00
Purchase #4	$170.29	12.514%	$191.6001	$191.60	$191.60	$191.60
Purchase #5	$99.30	13.287%	$112.494	$112.49	$112.50	$112.50
Purchase #6	$152.73	5.150%	$160.5956	$160.60	$160.60	$160.60
Purchase #7	$22.61	12.860%	$25.5176	$25.52	$25.50	$25.50
7 purchase totals =	$821.56		$901.7657	$901.77	$901.75	$901.70