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	$103.41	7.233%	$110.8896	$110.89	$110.90	$110.90
Purchase #2	$242.34	6.687%	$258.5453	$258.55	$258.55	$258.50
Purchase #3	$167.58	10.419%	$185.0402	$185.04	$185.05	$185.00
Purchase #4	$235.73	10.642%	$260.8164	$260.82	$260.80	$260.80
Purchase #5	$137.44	5.385%	$144.8411	$144.84	$144.85	$144.80
Purchase #6	$229.46	3.719%	$237.9936	$237.99	$238.00	$238.00
Purchase #7	$18.88	8.335%	$20.4536	$20.45	$20.45	$20.50
7 purchase totals =	$1,134.84		$1,218.5798	$1,218.58	$1,218.60	$1,218.50