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	$149.91	11.297%	$166.8453	$166.85	$166.85	$166.80
Purchase #2	$241.54	13.452%	$274.032	$274.03	$274.05	$274.00
Purchase #3	$39.70	9.239%	$43.3679	$43.37	$43.35	$43.40
Purchase #4	$173.50	3.192%	$179.0381	$179.04	$179.05	$179.00
Purchase #5	$139.36	8.675%	$151.4495	$151.45	$151.45	$151.40
Purchase #6	$153.54	5.722%	$162.3256	$162.33	$162.35	$162.30
Purchase #7	$144.62	6.448%	$153.9451	$153.95	$153.95	$153.90
7 purchase totals =	$1,042.17		$1,131.0035	$1,131.02	$1,131.05	$1,130.80