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	$57.66	3.376%	$59.6066	$59.61	$59.60	$59.60
Purchase #2	$20.34	6.567%	$21.6757	$21.68	$21.70	$21.70
Purchase #3	$116.65	9.132%	$127.3025	$127.30	$127.30	$127.30
Purchase #4	$98.84	13.189%	$111.876	$111.88	$111.90	$111.90
Purchase #5	$144.95	8.281%	$156.9533	$156.95	$156.95	$157.00
Purchase #6	$178.38	3.520%	$184.659	$184.66	$184.65	$184.70
Purchase #7	$70.88	10.665%	$78.4394	$78.44	$78.45	$78.40
7 purchase totals =	$687.70		$740.5125	$740.52	$740.55	$740.60