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	$114.61	10.426%	$126.5592	$126.56	$126.55	$126.60
Purchase #2	$227.32	11.523%	$253.5141	$253.51	$253.50	$253.50
Purchase #3	$216.60	13.343%	$245.5009	$245.50	$245.50	$245.50
Purchase #4	$223.66	4.188%	$233.0269	$233.03	$233.05	$233.00
Purchase #5	$220.75	13.709%	$251.0126	$251.01	$251.00	$251.00
Purchase #6	$96.70	4.277%	$100.8359	$100.84	$100.85	$100.80
Purchase #7	$134.87	13.393%	$152.9331	$152.93	$152.95	$152.90
7 purchase totals =	$1,234.51		$1,363.3827	$1,363.38	$1,363.40	$1,363.30