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	$88.60	13.826%	$100.8498	$100.85	$100.85	$100.80
Purchase #2	$112.75	5.313%	$118.7404	$118.74	$118.75	$118.70
Purchase #3	$87.74	4.779%	$91.9331	$91.93	$91.95	$91.90
Purchase #4	$41.82	4.541%	$43.719	$43.72	$43.70	$43.70
Purchase #5	$129.38	9.748%	$141.992	$141.99	$142.00	$142.00
Purchase #6	$240.26	6.662%	$256.2661	$256.27	$256.25	$256.30
Purchase #7	$205.54	11.112%	$228.3796	$228.38	$228.40	$228.40
7 purchase totals =	$906.09		$981.8800	$981.88	$981.90	$981.80