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	$165.58	3.579%	$171.5061	$171.51	$171.50	$171.50
Purchase #2	$12.44	9.478%	$13.6191	$13.62	$13.60	$13.60
Purchase #3	$48.89	12.183%	$54.8463	$54.85	$54.85	$54.80
Purchase #4	$35.73	4.768%	$37.4336	$37.43	$37.45	$37.40
Purchase #5	$148.35	9.203%	$162.0027	$162.00	$162.00	$162.00
Purchase #6	$7.90	10.369%	$8.7192	$8.72	$8.70	$8.70
Purchase #7	$32.61	13.552%	$37.0293	$37.03	$37.05	$37.00
7 purchase totals =	$451.50		$485.1563	$485.16	$485.15	$485.00