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	$222.80	13.866%	$253.6934	$253.69	$253.70	$253.70
Purchase #2	$101.39	4.424%	$105.8755	$105.88	$105.90	$105.90
Purchase #3	$6.86	6.555%	$7.3097	$7.31	$7.30	$7.30
Purchase #4	$207.71	3.247%	$214.4543	$214.45	$214.45	$214.50
Purchase #5	$104.58	10.543%	$115.6059	$115.61	$115.60	$115.60
Purchase #6	$186.89	5.314%	$196.8213	$196.82	$196.80	$196.80
Purchase #7	$246.74	6.382%	$262.4869	$262.49	$262.50	$262.50
7 purchase totals =	$1,076.97		$1,156.2470	$1,156.25	$1,156.25	$1,156.30