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	$93.67	6.379%	$99.6452	$99.65	$99.65	$99.60
Purchase #2	$9.62	7.281%	$10.3204	$10.32	$10.30	$10.30
Purchase #3	$150.88	12.511%	$169.7566	$169.76	$169.75	$169.80
Purchase #4	$101.30	11.239%	$112.6851	$112.69	$112.70	$112.70
Purchase #5	$123.34	3.659%	$127.853	$127.85	$127.85	$127.90
Purchase #6	$196.25	13.540%	$222.8223	$222.82	$222.80	$222.80
Purchase #7	$51.37	6.268%	$54.5899	$54.59	$54.60	$54.60
7 purchase totals =	$726.43		$797.6725	$797.68	$797.65	$797.70