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	$144.28	6.769%	$154.0463	$154.05	$154.05	$154.00
Purchase #2	$233.40	9.866%	$256.4272	$256.43	$256.45	$256.40
Purchase #3	$165.88	5.428%	$174.884	$174.88	$174.90	$174.90
Purchase #4	$47.69	7.761%	$51.3912	$51.39	$51.40	$51.40
Purchase #5	$73.83	5.221%	$77.6847	$77.68	$77.70	$77.70
Purchase #6	$163.33	6.293%	$173.6084	$173.61	$173.60	$173.60
Purchase #7	$235.45	11.438%	$262.3808	$262.38	$262.40	$262.40
7 purchase totals =	$1,063.86		$1,150.4226	$1,150.42	$1,150.50	$1,150.40