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	$43.82	7.632%	$47.1643	$47.16	$47.15	$47.20
Purchase #2	$9.29	8.158%	$10.0479	$10.05	$10.05	$10.00
Purchase #3	$12.53	6.133%	$13.2985	$13.30	$13.30	$13.30
Purchase #4	$237.57	9.227%	$259.4906	$259.49	$259.50	$259.50
Purchase #5	$30.79	12.219%	$34.5522	$34.55	$34.55	$34.60
Purchase #6	$100.89	10.456%	$111.4391	$111.44	$111.45	$111.40
Purchase #7	$133.88	5.557%	$141.3197	$141.32	$141.30	$141.30
7 purchase totals =	$568.77		$617.3123	$617.31	$617.30	$617.30