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	$205.53	8.716%	$223.444	$223.44	$223.45	$223.40
Purchase #2	$167.52	13.119%	$189.4969	$189.50	$189.50	$189.50
Purchase #3	$73.27	12.259%	$82.2522	$82.25	$82.25	$82.30
Purchase #4	$159.45	4.622%	$166.8198	$166.82	$166.80	$166.80
Purchase #5	$20.39	4.436%	$21.2945	$21.29	$21.30	$21.30
Purchase #6	$216.88	7.552%	$233.2588	$233.26	$233.25	$233.30
Purchase #7	$45.60	4.594%	$47.6949	$47.69	$47.70	$47.70
7 purchase totals =	$888.64		$964.2611	$964.25	$964.25	$964.30