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	$204.45	8.396%	$221.6156	$221.62	$221.60	$221.60
Purchase #2	$66.91	6.679%	$71.3789	$71.38	$71.40	$71.40
Purchase #3	$216.69	3.294%	$223.8278	$223.83	$223.85	$223.80
Purchase #4	$244.91	4.585%	$256.1391	$256.14	$256.15	$256.10
Purchase #5	$178.38	10.185%	$196.548	$196.55	$196.55	$196.50
Purchase #6	$13.74	12.281%	$15.4274	$15.43	$15.45	$15.40
Purchase #7	$112.59	11.554%	$125.5986	$125.60	$125.60	$125.60
7 purchase totals =	$1,037.67		$1,110.5354	$1,110.55	$1,110.60	$1,110.40