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	$224.53	5.834%	$237.6291	$237.63	$237.65	$237.60
Purchase #2	$143.75	11.438%	$160.1921	$160.19	$160.20	$160.20
Purchase #3	$138.50	4.442%	$144.6522	$144.65	$144.65	$144.70
Purchase #4	$88.64	4.211%	$92.3726	$92.37	$92.35	$92.40
Purchase #5	$64.54	12.279%	$72.4649	$72.46	$72.45	$72.50
Purchase #6	$89.53	12.345%	$100.5825	$100.58	$100.60	$100.60
Purchase #7	$118.70	7.368%	$127.4458	$127.45	$127.45	$127.40
7 purchase totals =	$868.19		$935.3392	$935.33	$935.35	$935.40