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	$233.83	5.371%	$246.389	$246.39	$246.40	$246.40
Purchase #2	$97.71	13.853%	$111.2458	$111.25	$111.25	$111.20
Purchase #3	$240.73	3.192%	$248.4141	$248.41	$248.40	$248.40
Purchase #4	$140.89	11.784%	$157.4925	$157.49	$157.50	$157.50
Purchase #5	$92.50	11.285%	$102.9386	$102.94	$102.95	$102.90
Purchase #6	$32.35	5.535%	$34.1406	$34.14	$34.15	$34.10
Purchase #7	$240.93	13.119%	$272.5376	$272.54	$272.55	$272.50
7 purchase totals =	$1,078.94		$1,173.1582	$1,173.16	$1,173.20	$1,173.00