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	$142.34	6.113%	$151.0412	$151.04	$151.05	$151.00
Purchase #2	$184.85	8.565%	$200.6824	$200.68	$200.70	$200.70
Purchase #3	$66.70	7.246%	$71.5331	$71.53	$71.55	$71.50
Purchase #4	$204.59	7.455%	$219.8422	$219.84	$219.85	$219.80
Purchase #5	$158.78	8.657%	$172.5256	$172.53	$172.55	$172.50
Purchase #6	$119.36	10.782%	$132.2294	$132.23	$132.25	$132.20
Purchase #7	$72.84	8.103%	$78.7422	$78.74	$78.75	$78.70
7 purchase totals =	$949.46		$1,026.5961	$1,026.59	$1,026.70	$1,026.40