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	$198.83	8.392%	$215.5158	$215.52	$215.50	$215.50
Purchase #2	$167.35	7.436%	$179.7941	$179.79	$179.80	$179.80
Purchase #3	$239.27	5.853%	$253.2745	$253.27	$253.25	$253.30
Purchase #4	$45.62	10.417%	$50.3722	$50.37	$50.35	$50.40
Purchase #5	$166.25	11.864%	$185.9739	$185.97	$185.95	$186.00
Purchase #6	$245.55	6.830%	$262.3211	$262.32	$262.30	$262.30
Purchase #7	$166.92	13.833%	$190.01	$190.01	$190.00	$190.00
7 purchase totals =	$1,229.79		$1,337.2616	$1,337.25	$1,337.15	$1,337.30