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	$65.97	4.784%	$69.126	$69.13	$69.15	$69.10
Purchase #2	$51.50	6.820%	$55.0123	$55.01	$55.00	$55.00
Purchase #3	$37.99	13.458%	$43.1027	$43.10	$43.10	$43.10
Purchase #4	$91.35	11.278%	$101.6525	$101.65	$101.65	$101.70
Purchase #5	$152.52	13.666%	$173.3634	$173.36	$173.35	$173.40
Purchase #6	$105.47	5.579%	$111.3542	$111.35	$111.35	$111.40
Purchase #7	$161.33	13.401%	$182.9498	$182.95	$182.95	$182.90
7 purchase totals =	$666.13		$736.5609	$736.55	$736.55	$736.60