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	$47.48	8.591%	$51.559	$51.56	$51.55	$51.60
Purchase #2	$41.93	7.735%	$45.1733	$45.17	$45.15	$45.20
Purchase #3	$59.73	4.697%	$62.5355	$62.54	$62.55	$62.50
Purchase #4	$213.57	6.286%	$226.995	$227.00	$227.00	$227.00
Purchase #5	$36.41	3.286%	$37.6064	$37.61	$37.60	$37.60
Purchase #6	$80.80	3.239%	$83.4171	$83.42	$83.40	$83.40
Purchase #7	$108.59	11.621%	$121.2092	$121.21	$121.20	$121.20
7 purchase totals =	$588.51		$628.4955	$628.51	$628.45	$628.50