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	$158.67	5.527%	$167.4397	$167.44	$167.45	$167.40
Purchase #2	$27.57	5.417%	$29.0635	$29.06	$29.05	$29.10
Purchase #3	$222.87	12.834%	$251.4731	$251.47	$251.45	$251.50
Purchase #4	$17.36	4.834%	$18.1992	$18.20	$18.20	$18.20
Purchase #5	$193.60	3.650%	$200.6664	$200.67	$200.65	$200.70
Purchase #6	$85.67	4.710%	$89.7051	$89.71	$89.70	$89.70
Purchase #7	$57.49	3.293%	$59.3831	$59.38	$59.40	$59.40
7 purchase totals =	$763.23		$815.9301	$815.93	$815.90	$816.00