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	$229.97	10.518%	$254.1582	$254.16	$254.15	$254.20
Purchase #2	$192.70	7.184%	$206.5436	$206.54	$206.55	$206.50
Purchase #3	$30.40	5.755%	$32.1495	$32.15	$32.15	$32.10
Purchase #4	$94.73	5.163%	$99.6209	$99.62	$99.60	$99.60
Purchase #5	$208.80	10.684%	$231.1082	$231.11	$231.10	$231.10
Purchase #6	$136.74	8.494%	$148.3547	$148.35	$148.35	$148.40
Purchase #7	$103.76	7.496%	$111.5378	$111.54	$111.55	$111.50
7 purchase totals =	$997.10		$1,083.4729	$1,083.47	$1,083.45	$1,083.40