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	$70.45	11.386%	$78.4714	$78.47	$78.45	$78.50
Purchase #2	$77.88	11.169%	$86.5784	$86.58	$86.60	$86.60
Purchase #3	$11.35	3.786%	$11.7797	$11.78	$11.80	$11.80
Purchase #4	$106.69	5.314%	$112.3595	$112.36	$112.35	$112.40
Purchase #5	$223.52	4.427%	$233.4152	$233.42	$233.40	$233.40
Purchase #6	$221.69	10.777%	$245.5815	$245.58	$245.60	$245.60
Purchase #7	$247.58	10.376%	$273.2689	$273.27	$273.25	$273.30
7 purchase totals =	$959.16		$1,041.4546	$1,041.46	$1,041.45	$1,041.60