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	$21.87	4.166%	$22.7811	$22.78	$22.80	$22.80
Purchase #2	$23.54	7.341%	$25.2681	$25.27	$25.25	$25.30
Purchase #3	$94.78	5.868%	$100.3417	$100.34	$100.35	$100.30
Purchase #4	$241.54	12.312%	$271.2784	$271.28	$271.30	$271.30
Purchase #5	$131.91	5.469%	$139.1242	$139.12	$139.10	$139.10
Purchase #6	$60.97	10.636%	$67.4548	$67.45	$67.45	$67.50
Purchase #7	$71.83	3.223%	$74.1451	$74.15	$74.15	$74.10
7 purchase totals =	$646.44		$700.3934	$700.39	$700.40	$700.40