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	$33.34	13.711%	$37.9112	$37.91	$37.90	$37.90
Purchase #2	$15.35	12.691%	$17.2981	$17.30	$17.30	$17.30
Purchase #3	$68.32	6.183%	$72.5442	$72.54	$72.55	$72.50
Purchase #4	$34.66	3.208%	$35.7719	$35.77	$35.75	$35.80
Purchase #5	$54.87	3.562%	$56.8245	$56.82	$56.80	$56.80
Purchase #6	$123.89	12.805%	$139.7541	$139.75	$139.75	$139.80
Purchase #7	$43.60	12.599%	$49.0932	$49.09	$49.10	$49.10
7 purchase totals =	$374.03		$409.1972	$409.18	$409.15	$409.20