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	$69.54	3.665%	$72.0886	$72.09	$72.10	$72.10
Purchase #2	$119.61	12.423%	$134.4692	$134.47	$134.45	$134.50
Purchase #3	$119.42	11.440%	$133.0816	$133.08	$133.10	$133.10
Purchase #4	$71.81	8.798%	$78.1278	$78.13	$78.15	$78.10
Purchase #5	$233.61	3.585%	$241.9849	$241.98	$242.00	$242.00
Purchase #6	$135.76	4.342%	$141.6547	$141.65	$141.65	$141.70
Purchase #7	$129.73	13.103%	$146.7285	$146.73	$146.75	$146.70
7 purchase totals =	$879.48		$948.1353	$948.13	$948.20	$948.20