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	$143.59	6.559%	$153.0081	$153.01	$153.00	$153.00
Purchase #2	$18.66	13.426%	$21.1653	$21.17	$21.15	$21.20
Purchase #3	$91.73	13.808%	$104.3961	$104.40	$104.40	$104.40
Purchase #4	$107.87	7.685%	$116.1598	$116.16	$116.15	$116.20
Purchase #5	$227.39	6.124%	$241.3154	$241.32	$241.30	$241.30
Purchase #6	$42.69	4.218%	$44.4907	$44.49	$44.50	$44.50
Purchase #7	$67.78	5.577%	$71.5601	$71.56	$71.55	$71.60
7 purchase totals =	$699.71		$752.0955	$752.11	$752.05	$752.20