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	$156.89	7.835%	$169.1823	$169.18	$169.20	$169.20
Purchase #2	$98.96	8.552%	$107.4231	$107.42	$107.40	$107.40
Purchase #3	$35.82	4.356%	$37.3803	$37.38	$37.40	$37.40
Purchase #4	$149.65	13.283%	$169.528	$169.53	$169.55	$169.50
Purchase #5	$157.34	9.816%	$172.7845	$172.78	$172.80	$172.80
Purchase #6	$60.32	11.169%	$67.0571	$67.06	$67.05	$67.10
Purchase #7	$151.66	4.491%	$158.4711	$158.47	$158.45	$158.50
7 purchase totals =	$810.64		$881.8264	$881.82	$881.85	$881.90