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	$225.48	3.764%	$233.9671	$233.97	$233.95	$234.00
Purchase #2	$48.51	3.545%	$50.2297	$50.23	$50.25	$50.20
Purchase #3	$137.74	5.149%	$144.8322	$144.83	$144.85	$144.80
Purchase #4	$58.56	5.185%	$61.5963	$61.60	$61.60	$61.60
Purchase #5	$149.70	9.732%	$164.2688	$164.27	$164.25	$164.30
Purchase #6	$150.50	10.746%	$166.6727	$166.67	$166.65	$166.70
Purchase #7	$131.99	3.485%	$136.5899	$136.59	$136.60	$136.60
7 purchase totals =	$902.48		$958.1567	$958.16	$958.15	$958.20