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	$112.50	3.367%	$116.2879	$116.29	$116.30	$116.30
Purchase #2	$105.64	10.685%	$116.9276	$116.93	$116.95	$116.90
Purchase #3	$173.89	11.473%	$193.8404	$193.84	$193.85	$193.80
Purchase #4	$73.93	5.415%	$77.9333	$77.93	$77.95	$77.90
Purchase #5	$217.28	10.737%	$240.6094	$240.61	$240.60	$240.60
Purchase #6	$90.67	5.732%	$95.8672	$95.87	$95.85	$95.90
Purchase #7	$68.32	4.747%	$71.5632	$71.56	$71.55	$71.60
7 purchase totals =	$842.23		$913.0290	$913.03	$913.05	$913.00