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	$42.26	4.368%	$44.1059	$44.11	$44.10	$44.10
Purchase #2	$49.75	8.270%	$53.8643	$53.86	$53.85	$53.90
Purchase #3	$151.86	4.663%	$158.9412	$158.94	$158.95	$158.90
Purchase #4	$77.97	7.302%	$83.6634	$83.66	$83.65	$83.70
Purchase #5	$54.80	9.393%	$59.9474	$59.95	$59.95	$59.90
Purchase #6	$207.93	3.506%	$215.22	$215.22	$215.20	$215.20
Purchase #7	$37.68	7.334%	$40.4435	$40.44	$40.45	$40.40
7 purchase totals =	$622.25		$656.1857	$656.18	$656.15	$656.10