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	$210.49	12.154%	$236.073	$236.07	$236.05	$236.10
Purchase #2	$96.79	4.206%	$100.861	$100.86	$100.85	$100.90
Purchase #3	$102.94	4.787%	$107.8677	$107.87	$107.85	$107.90
Purchase #4	$247.74	8.636%	$269.1348	$269.13	$269.15	$269.10
Purchase #5	$87.51	13.535%	$99.3545	$99.35	$99.35	$99.40
Purchase #6	$99.91	11.580%	$111.4796	$111.48	$111.50	$111.50
Purchase #7	$60.34	7.774%	$65.0308	$65.03	$65.05	$65.00
7 purchase totals =	$905.72		$989.8014	$989.79	$989.80	$989.90