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	$158.93	13.212%	$179.9278	$179.93	$179.95	$179.90
Purchase #2	$185.72	13.405%	$210.6158	$210.62	$210.60	$210.60
Purchase #3	$221.97	10.566%	$245.4234	$245.42	$245.40	$245.40
Purchase #4	$92.87	12.414%	$104.3989	$104.40	$104.40	$104.40
Purchase #5	$141.61	13.644%	$160.9313	$160.93	$160.95	$160.90
Purchase #6	$141.62	6.105%	$150.2659	$150.27	$150.25	$150.30
Purchase #7	$124.89	3.319%	$129.0351	$129.04	$129.05	$129.00
7 purchase totals =	$1,067.61		$1,180.5982	$1,180.61	$1,180.60	$1,180.50