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	$13.46	7.478%	$14.4665	$14.47	$14.45	$14.50
Purchase #2	$87.60	4.102%	$91.1934	$91.19	$91.20	$91.20
Purchase #3	$47.59	8.472%	$51.6218	$51.62	$51.60	$51.60
Purchase #4	$89.30	10.819%	$98.9614	$98.96	$98.95	$99.00
Purchase #5	$178.73	4.248%	$186.3225	$186.32	$186.30	$186.30
Purchase #6	$63.78	11.548%	$71.1453	$71.15	$71.15	$71.10
Purchase #7	$172.43	13.874%	$196.3529	$196.35	$196.35	$196.40
7 purchase totals =	$652.89		$710.0638	$710.06	$710.00	$710.10