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	$224.92	5.579%	$237.4683	$237.47	$237.45	$237.50
Purchase #2	$58.78	3.839%	$61.0366	$61.04	$61.05	$61.00
Purchase #3	$96.62	10.464%	$106.7303	$106.73	$106.75	$106.70
Purchase #4	$51.82	8.128%	$56.0319	$56.03	$56.05	$56.00
Purchase #5	$166.91	11.201%	$185.6056	$185.61	$185.60	$185.60
Purchase #6	$33.30	12.410%	$37.4325	$37.43	$37.45	$37.40
Purchase #7	$42.67	7.532%	$45.8839	$45.88	$45.90	$45.90
7 purchase totals =	$675.02		$730.1891	$730.19	$730.25	$730.10