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	$14.59	11.719%	$16.2998	$16.30	$16.30	$16.30
Purchase #2	$61.98	13.770%	$70.5146	$70.51	$70.50	$70.50
Purchase #3	$64.53	5.103%	$67.823	$67.82	$67.80	$67.80
Purchase #4	$82.55	10.797%	$91.4629	$91.46	$91.45	$91.50
Purchase #5	$240.35	12.408%	$270.1726	$270.17	$270.15	$270.20
Purchase #6	$72.40	8.870%	$78.8219	$78.82	$78.80	$78.80
Purchase #7	$31.90	5.256%	$33.5767	$33.58	$33.60	$33.60
7 purchase totals =	$568.30		$628.6715	$628.66	$628.60	$628.70