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	$162.77	9.542%	$178.3015	$178.30	$178.30	$178.30
Purchase #2	$246.45	8.180%	$266.6096	$266.61	$266.60	$266.60
Purchase #3	$174.67	8.609%	$189.7073	$189.71	$189.70	$189.70
Purchase #4	$52.81	3.161%	$54.4793	$54.48	$54.50	$54.50
Purchase #5	$85.32	6.536%	$90.8965	$90.90	$90.90	$90.90
Purchase #6	$71.73	5.141%	$75.4176	$75.42	$75.40	$75.40
Purchase #7	$205.43	5.744%	$217.2299	$217.23	$217.25	$217.20
7 purchase totals =	$999.18		$1,072.6417	$1,072.65	$1,072.65	$1,072.60