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	$233.42	5.405%	$246.0364	$246.04	$246.05	$246.00
Purchase #2	$102.68	8.355%	$111.2589	$111.26	$111.25	$111.30
Purchase #3	$16.77	13.330%	$19.0054	$19.01	$19.00	$19.00
Purchase #4	$123.76	12.829%	$139.6372	$139.64	$139.65	$139.60
Purchase #5	$249.81	9.295%	$273.0298	$273.03	$273.05	$273.00
Purchase #6	$109.71	4.250%	$114.3727	$114.37	$114.35	$114.40
Purchase #7	$137.45	10.287%	$151.5895	$151.59	$151.60	$151.60
7 purchase totals =	$973.60		$1,054.9299	$1,054.94	$1,054.95	$1,054.90