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	$134.53	7.475%	$144.5861	$144.59	$144.60	$144.60
Purchase #2	$200.68	5.220%	$211.1555	$211.16	$211.15	$211.20
Purchase #3	$160.28	8.141%	$173.3284	$173.33	$173.35	$173.30
Purchase #4	$128.46	6.256%	$136.4965	$136.50	$136.50	$136.50
Purchase #5	$150.51	12.325%	$169.0604	$169.06	$169.05	$169.10
Purchase #6	$22.52	13.245%	$25.5028	$25.50	$25.50	$25.50
Purchase #7	$174.42	6.543%	$185.8323	$185.83	$185.85	$185.80
7 purchase totals =	$971.40		$1,045.9620	$1,045.97	$1,046.00	$1,046.00