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	$60.48	3.213%	$62.4232	$62.42	$62.40	$62.40
Purchase #2	$37.44	10.149%	$41.2398	$41.24	$41.25	$41.20
Purchase #3	$128.30	8.712%	$139.4775	$139.48	$139.50	$139.50
Purchase #4	$198.47	12.229%	$222.7409	$222.74	$222.75	$222.70
Purchase #5	$27.59	3.610%	$28.586	$28.59	$28.60	$28.60
Purchase #6	$223.70	3.160%	$230.7689	$230.77	$230.75	$230.80
Purchase #7	$116.33	5.864%	$123.1516	$123.15	$123.15	$123.20
7 purchase totals =	$792.31		$848.3879	$848.39	$848.40	$848.40