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	$162.75	6.257%	$172.9333	$172.93	$172.95	$172.90
Purchase #2	$58.58	13.512%	$66.4953	$66.50	$66.50	$66.50
Purchase #3	$48.86	10.796%	$54.1349	$54.13	$54.15	$54.10
Purchase #4	$226.30	12.646%	$254.9179	$254.92	$254.90	$254.90
Purchase #5	$239.97	12.803%	$270.6934	$270.69	$270.70	$270.70
Purchase #6	$140.28	7.214%	$150.3998	$150.40	$150.40	$150.40
Purchase #7	$143.66	13.422%	$162.942	$162.94	$162.95	$162.90
7 purchase totals =	$1,020.40		$1,132.5166	$1,132.51	$1,132.55	$1,132.40