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	$34.49	8.602%	$37.4568	$37.46	$37.45	$37.50
Purchase #2	$89.47	10.328%	$98.7105	$98.71	$98.70	$98.70
Purchase #3	$112.46	5.765%	$118.9433	$118.94	$118.95	$118.90
Purchase #4	$147.78	3.171%	$152.4661	$152.47	$152.45	$152.50
Purchase #5	$130.33	5.452%	$137.4356	$137.44	$137.45	$137.40
Purchase #6	$66.51	11.362%	$74.0669	$74.07	$74.05	$74.10
Purchase #7	$128.37	6.698%	$136.9682	$136.97	$136.95	$137.00
7 purchase totals =	$709.41		$756.0474	$756.06	$756.00	$756.10