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	$235.72	8.280%	$255.2376	$255.24	$255.25	$255.20
Purchase #2	$189.72	12.594%	$213.6133	$213.61	$213.60	$213.60
Purchase #3	$92.58	3.111%	$95.4602	$95.46	$95.45	$95.50
Purchase #4	$235.89	7.316%	$253.1477	$253.15	$253.15	$253.10
Purchase #5	$132.39	4.285%	$138.0629	$138.06	$138.05	$138.10
Purchase #6	$18.96	4.710%	$19.853	$19.85	$19.85	$19.90
Purchase #7	$52.84	9.870%	$58.0553	$58.06	$58.05	$58.10
7 purchase totals =	$958.10		$1,033.4300	$1,033.43	$1,033.40	$1,033.50