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	$133.30	9.195%	$145.5569	$145.56	$145.55	$145.60
Purchase #2	$167.85	13.291%	$190.1589	$190.16	$190.15	$190.20
Purchase #3	$172.92	11.788%	$193.3038	$193.30	$193.30	$193.30
Purchase #4	$129.59	6.144%	$137.552	$137.55	$137.55	$137.60
Purchase #5	$49.66	11.663%	$55.4518	$55.45	$55.45	$55.50
Purchase #6	$182.72	3.582%	$189.265	$189.27	$189.25	$189.30
Purchase #7	$16.52	10.602%	$18.2715	$18.27	$18.25	$18.30
7 purchase totals =	$852.56		$929.5599	$929.56	$929.50	$929.80