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	$124.93	5.546%	$131.8586	$131.86	$131.85	$131.90
Purchase #2	$183.41	4.385%	$191.4525	$191.45	$191.45	$191.50
Purchase #3	$112.54	9.758%	$123.5217	$123.52	$123.50	$123.50
Purchase #4	$50.87	11.234%	$56.5847	$56.58	$56.60	$56.60
Purchase #5	$21.93	3.837%	$22.7715	$22.77	$22.75	$22.80
Purchase #6	$120.42	8.338%	$130.4606	$130.46	$130.45	$130.50
Purchase #7	$161.96	4.292%	$168.9113	$168.91	$168.90	$168.90
7 purchase totals =	$776.06		$825.5609	$825.55	$825.50	$825.70