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	$54.98	7.431%	$59.0656	$59.07	$59.05	$59.10
Purchase #2	$144.33	11.640%	$161.13	$161.13	$161.15	$161.10
Purchase #3	$103.59	13.387%	$117.4576	$117.46	$117.45	$117.50
Purchase #4	$50.41	13.293%	$57.111	$57.11	$57.10	$57.10
Purchase #5	$164.70	4.841%	$172.6731	$172.67	$172.65	$172.70
Purchase #6	$250.58	12.698%	$282.3986	$282.40	$282.40	$282.40
Purchase #7	$26.30	10.124%	$28.9626	$28.96	$28.95	$29.00
7 purchase totals =	$794.89		$878.7985	$878.80	$878.75	$878.90