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	$108.28	7.526%	$116.4292	$116.43	$116.45	$116.40
Purchase #2	$85.88	4.216%	$89.5007	$89.50	$89.50	$89.50
Purchase #3	$153.71	9.801%	$168.7751	$168.78	$168.80	$168.80
Purchase #4	$211.63	5.618%	$223.5194	$223.52	$223.50	$223.50
Purchase #5	$247.60	13.555%	$281.1622	$281.16	$281.15	$281.20
Purchase #6	$211.59	5.790%	$223.8411	$223.84	$223.85	$223.80
Purchase #7	$157.98	3.278%	$163.1586	$163.16	$163.15	$163.20
7 purchase totals =	$1,176.67		$1,266.3863	$1,266.39	$1,266.40	$1,266.40