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	$24.55	3.642%	$25.4441	$25.44	$25.45	$25.40
Purchase #2	$244.91	10.485%	$270.5888	$270.59	$270.60	$270.60
Purchase #3	$49.58	10.109%	$54.592	$54.59	$54.60	$54.60
Purchase #4	$223.59	6.273%	$237.6158	$237.62	$237.60	$237.60
Purchase #5	$136.27	10.127%	$150.0701	$150.07	$150.05	$150.10
Purchase #6	$174.60	11.437%	$194.569	$194.57	$194.55	$194.60
Purchase #7	$224.99	13.609%	$255.6089	$255.61	$255.60	$255.60
7 purchase totals =	$1,078.49		$1,188.4887	$1,188.49	$1,188.45	$1,188.50