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	$241.74	5.662%	$255.4273	$255.43	$255.45	$255.40
Purchase #2	$235.73	7.527%	$253.4734	$253.47	$253.45	$253.50
Purchase #3	$139.38	9.476%	$152.5876	$152.59	$152.60	$152.60
Purchase #4	$104.62	4.671%	$109.5068	$109.51	$109.50	$109.50
Purchase #5	$217.92	4.152%	$226.968	$226.97	$226.95	$227.00
Purchase #6	$81.95	7.234%	$87.8783	$87.88	$87.90	$87.90
Purchase #7	$148.56	12.731%	$167.4732	$167.47	$167.45	$167.50
7 purchase totals =	$1,169.90		$1,253.3146	$1,253.32	$1,253.30	$1,253.40