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	$79.39	10.553%	$87.768	$87.77	$87.75	$87.80
Purchase #2	$86.30	7.138%	$92.4601	$92.46	$92.45	$92.50
Purchase #3	$240.53	9.660%	$263.7652	$263.77	$263.75	$263.80
Purchase #4	$126.82	11.605%	$141.5375	$141.54	$141.55	$141.50
Purchase #5	$76.31	12.465%	$85.822	$85.82	$85.80	$85.80
Purchase #6	$25.97	5.858%	$27.4913	$27.49	$27.50	$27.50
Purchase #7	$224.63	13.709%	$255.4245	$255.42	$255.40	$255.40
7 purchase totals =	$859.95		$954.2686	$954.27	$954.20	$954.30