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	$31.35	10.823%	$34.743	$34.74	$34.75	$34.70
Purchase #2	$200.73	11.264%	$223.3402	$223.34	$223.35	$223.30
Purchase #3	$127.42	3.624%	$132.0377	$132.04	$132.05	$132.00
Purchase #4	$162.55	12.281%	$182.5128	$182.51	$182.50	$182.50
Purchase #5	$44.81	6.663%	$47.7957	$47.80	$47.80	$47.80
Purchase #6	$33.36	12.696%	$37.5954	$37.60	$37.60	$37.60
Purchase #7	$114.54	11.452%	$127.6571	$127.66	$127.65	$127.70
7 purchase totals =	$714.76		$785.6819	$785.69	$785.70	$785.60