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	$149.83	6.171%	$159.076	$159.08	$159.10	$159.10
Purchase #2	$166.49	8.410%	$180.4918	$180.49	$180.50	$180.50
Purchase #3	$155.39	12.524%	$174.851	$174.85	$174.85	$174.90
Purchase #4	$206.67	4.162%	$215.2716	$215.27	$215.25	$215.30
Purchase #5	$61.42	10.169%	$67.6658	$67.67	$67.65	$67.70
Purchase #6	$55.36	7.396%	$59.4544	$59.45	$59.45	$59.50
Purchase #7	$140.53	13.833%	$159.9695	$159.97	$159.95	$160.00
7 purchase totals =	$935.69		$1,016.7801	$1,016.78	$1,016.75	$1,017.00