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	$63.50	10.769%	$70.3383	$70.34	$70.35	$70.30
Purchase #2	$13.81	4.273%	$14.4001	$14.40	$14.40	$14.40
Purchase #3	$237.77	11.704%	$265.5986	$265.60	$265.60	$265.60
Purchase #4	$153.66	12.258%	$172.4956	$172.50	$172.50	$172.50
Purchase #5	$134.46	12.415%	$151.1532	$151.15	$151.15	$151.20
Purchase #6	$97.74	9.811%	$107.3293	$107.33	$107.35	$107.30
Purchase #7	$231.51	3.188%	$238.8905	$238.89	$238.90	$238.90
7 purchase totals =	$932.45		$1,020.2056	$1,020.21	$1,020.25	$1,020.20