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	$159.85	6.631%	$170.4497	$170.45	$170.45	$170.40
Purchase #2	$213.54	6.573%	$227.576	$227.58	$227.60	$227.60
Purchase #3	$166.59	7.804%	$179.5907	$179.59	$179.60	$179.60
Purchase #4	$199.27	13.857%	$226.8828	$226.88	$226.90	$226.90
Purchase #5	$85.89	10.312%	$94.747	$94.75	$94.75	$94.70
Purchase #6	$231.25	4.524%	$241.7118	$241.71	$241.70	$241.70
Purchase #7	$144.55	11.308%	$160.8957	$160.90	$160.90	$160.90
7 purchase totals =	$1,200.94		$1,301.8537	$1,301.86	$1,301.90	$1,301.80