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	$108.38	7.823%	$116.8586	$116.86	$116.85	$116.90
Purchase #2	$195.28	8.627%	$212.1268	$212.13	$212.15	$212.10
Purchase #3	$46.29	11.374%	$51.555	$51.56	$51.55	$51.60
Purchase #4	$90.61	9.348%	$99.0802	$99.08	$99.10	$99.10
Purchase #5	$7.83	13.748%	$8.9065	$8.91	$8.90	$8.90
Purchase #6	$83.96	11.627%	$93.722	$93.72	$93.70	$93.70
Purchase #7	$149.47	11.658%	$166.8952	$166.90	$166.90	$166.90
7 purchase totals =	$681.82		$749.1443	$749.16	$749.15	$749.20