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	$196.82	6.639%	$209.8869	$209.89	$209.90	$209.90
Purchase #2	$44.41	13.859%	$50.5648	$50.56	$50.55	$50.60
Purchase #3	$200.89	10.720%	$222.4254	$222.43	$222.45	$222.40
Purchase #4	$154.69	7.739%	$166.6615	$166.66	$166.65	$166.70
Purchase #5	$16.40	8.268%	$17.756	$17.76	$17.75	$17.80
Purchase #6	$56.70	5.357%	$59.7374	$59.74	$59.75	$59.70
Purchase #7	$119.32	10.730%	$132.123	$132.12	$132.10	$132.10
7 purchase totals =	$789.23		$859.1550	$859.16	$859.15	$859.20