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	$173.47	6.668%	$185.037	$185.04	$185.05	$185.00
Purchase #2	$125.31	4.113%	$130.464	$130.46	$130.45	$130.50
Purchase #3	$40.63	4.865%	$42.6066	$42.61	$42.60	$42.60
Purchase #4	$248.73	12.612%	$280.0998	$280.10	$280.10	$280.10
Purchase #5	$160.29	8.154%	$173.36	$173.36	$173.35	$173.40
Purchase #6	$49.56	5.785%	$52.427	$52.43	$52.45	$52.40
Purchase #7	$127.30	13.594%	$144.6052	$144.61	$144.60	$144.60
7 purchase totals =	$925.29		$1,008.5996	$1,008.61	$1,008.60	$1,008.60