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	$62.50	4.201%	$65.1256	$65.13	$65.15	$65.10
Purchase #2	$132.89	9.199%	$145.1146	$145.11	$145.10	$145.10
Purchase #3	$221.78	13.233%	$251.1281	$251.13	$251.15	$251.10
Purchase #4	$37.99	8.314%	$41.1485	$41.15	$41.15	$41.10
Purchase #5	$153.82	3.233%	$158.793	$158.79	$158.80	$158.80
Purchase #6	$69.84	12.818%	$78.7921	$78.79	$78.80	$78.80
Purchase #7	$63.50	7.811%	$68.46	$68.46	$68.45	$68.50
7 purchase totals =	$742.32		$808.5619	$808.56	$808.60	$808.50