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	$172.90	6.343%	$183.867	$183.87	$183.85	$183.90
Purchase #2	$13.82	8.141%	$14.9451	$14.95	$14.95	$14.90
Purchase #3	$209.60	9.600%	$229.7216	$229.72	$229.70	$229.70
Purchase #4	$37.54	7.746%	$40.4478	$40.45	$40.45	$40.40
Purchase #5	$98.66	11.644%	$110.148	$110.15	$110.15	$110.10
Purchase #6	$234.30	4.640%	$245.1715	$245.17	$245.15	$245.20
Purchase #7	$230.60	10.864%	$255.6524	$255.65	$255.65	$255.70
7 purchase totals =	$997.42		$1,079.9534	$1,079.96	$1,079.90	$1,079.90