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	$184.89	7.370%	$198.5164	$198.52	$198.50	$198.50
Purchase #2	$158.56	9.385%	$173.4409	$173.44	$173.45	$173.40
Purchase #3	$140.94	11.257%	$156.8056	$156.81	$156.80	$156.80
Purchase #4	$211.55	5.264%	$222.686	$222.69	$222.70	$222.70
Purchase #5	$12.54	12.872%	$14.1541	$14.15	$14.15	$14.20
Purchase #6	$95.95	8.103%	$103.7248	$103.72	$103.70	$103.70
Purchase #7	$218.95	12.105%	$245.4539	$245.45	$245.45	$245.50
7 purchase totals =	$1,023.38		$1,114.7817	$1,114.78	$1,114.75	$1,114.80