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	$65.55	10.326%	$72.3187	$72.32	$72.30	$72.30
Purchase #2	$35.76	10.801%	$39.6224	$39.62	$39.60	$39.60
Purchase #3	$60.60	5.381%	$63.8609	$63.86	$63.85	$63.90
Purchase #4	$210.27	4.328%	$219.3705	$219.37	$219.35	$219.40
Purchase #5	$216.70	8.140%	$234.3394	$234.34	$234.35	$234.30
Purchase #6	$245.63	11.314%	$273.4206	$273.42	$273.40	$273.40
Purchase #7	$227.40	6.113%	$241.301	$241.30	$241.30	$241.30
7 purchase totals =	$1,061.91		$1,144.2335	$1,144.23	$1,144.15	$1,144.20