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	$33.66	12.613%	$37.9055	$37.91	$37.90	$37.90
Purchase #2	$56.47	11.333%	$62.8697	$62.87	$62.85	$62.90
Purchase #3	$77.75	5.343%	$81.9042	$81.90	$81.90	$81.90
Purchase #4	$193.32	3.517%	$200.1191	$200.12	$200.10	$200.10
Purchase #5	$14.71	12.665%	$16.573	$16.57	$16.55	$16.60
Purchase #6	$16.58	11.359%	$18.4633	$18.46	$18.45	$18.50
Purchase #7	$16.36	6.467%	$17.418	$17.42	$17.40	$17.40
7 purchase totals =	$408.85		$435.2528	$435.25	$435.15	$435.30