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	$160.92	4.165%	$167.6223	$167.62	$167.60	$167.60
Purchase #2	$55.33	8.138%	$59.8328	$59.83	$59.85	$59.80
Purchase #3	$56.85	5.606%	$60.037	$60.04	$60.05	$60.00
Purchase #4	$151.81	5.107%	$159.5629	$159.56	$159.55	$159.60
Purchase #5	$218.72	3.608%	$226.6114	$226.61	$226.60	$226.60
Purchase #6	$95.94	7.627%	$103.2573	$103.26	$103.25	$103.30
Purchase #7	$10.86	9.815%	$11.9259	$11.93	$11.95	$11.90
7 purchase totals =	$750.43		$788.8496	$788.85	$788.85	$788.80