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	$49.81	3.366%	$51.4866	$51.49	$51.50	$51.50
Purchase #2	$76.78	9.287%	$83.9106	$83.91	$83.90	$83.90
Purchase #3	$84.46	9.426%	$92.4212	$92.42	$92.40	$92.40
Purchase #4	$54.37	12.706%	$61.2783	$61.28	$61.30	$61.30
Purchase #5	$103.72	6.391%	$110.3487	$110.35	$110.35	$110.30
Purchase #6	$166.68	3.716%	$172.8738	$172.87	$172.85	$172.90
Purchase #7	$127.65	4.392%	$133.2564	$133.26	$133.25	$133.30
7 purchase totals =	$663.47		$705.5756	$705.58	$705.55	$705.60