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	$84.83	6.705%	$90.5179	$90.52	$90.50	$90.50
Purchase #2	$96.74	4.553%	$101.1446	$101.14	$101.15	$101.10
Purchase #3	$117.58	7.832%	$126.7889	$126.79	$126.80	$126.80
Purchase #4	$164.98	3.410%	$170.6058	$170.61	$170.60	$170.60
Purchase #5	$229.47	10.431%	$253.406	$253.41	$253.40	$253.40
Purchase #6	$152.76	13.363%	$173.1733	$173.17	$173.15	$173.20
Purchase #7	$133.70	6.227%	$142.0255	$142.03	$142.05	$142.00
7 purchase totals =	$980.06		$1,057.6620	$1,057.67	$1,057.65	$1,057.60