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	$156.63	8.433%	$169.8386	$169.84	$169.85	$169.80
Purchase #2	$129.55	11.135%	$143.9754	$143.98	$144.00	$144.00
Purchase #3	$42.71	4.189%	$44.4991	$44.50	$44.50	$44.50
Purchase #4	$50.30	9.119%	$54.8869	$54.89	$54.90	$54.90
Purchase #5	$58.57	7.113%	$62.7361	$62.74	$62.75	$62.70
Purchase #6	$37.58	3.434%	$38.8705	$38.87	$38.85	$38.90
Purchase #7	$152.71	6.422%	$162.517	$162.52	$162.50	$162.50
7 purchase totals =	$628.05		$677.3236	$677.34	$677.35	$677.30