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	$51.47	7.591%	$55.3771	$55.38	$55.40	$55.40
Purchase #2	$174.95	9.146%	$190.9509	$190.95	$190.95	$191.00
Purchase #3	$214.77	3.613%	$222.5296	$222.53	$222.55	$222.50
Purchase #4	$150.87	12.826%	$170.2206	$170.22	$170.20	$170.20
Purchase #5	$248.32	9.603%	$272.1662	$272.17	$272.15	$272.20
Purchase #6	$68.91	5.628%	$72.7883	$72.79	$72.80	$72.80
Purchase #7	$191.38	10.666%	$211.7926	$211.79	$211.80	$211.80
7 purchase totals =	$1,100.67		$1,195.8253	$1,195.83	$1,195.85	$1,195.90