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	$33.92	4.550%	$35.4634	$35.46	$35.45	$35.50
Purchase #2	$122.61	3.709%	$127.1576	$127.16	$127.15	$127.20
Purchase #3	$9.99	8.725%	$10.8616	$10.86	$10.85	$10.90
Purchase #4	$169.77	9.415%	$185.7538	$185.75	$185.75	$185.80
Purchase #5	$203.41	9.263%	$222.2519	$222.25	$222.25	$222.30
Purchase #6	$167.52	13.667%	$190.415	$190.42	$190.40	$190.40
Purchase #7	$120.42	3.393%	$124.5059	$124.51	$124.50	$124.50
7 purchase totals =	$827.64		$896.4092	$896.41	$896.35	$896.60