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	$75.88	13.140%	$85.8506	$85.85	$85.85	$85.90
Purchase #2	$99.30	4.238%	$103.5083	$103.51	$103.50	$103.50
Purchase #3	$92.66	10.685%	$102.5607	$102.56	$102.55	$102.60
Purchase #4	$34.74	5.344%	$36.5965	$36.60	$36.60	$36.60
Purchase #5	$235.36	4.848%	$246.7703	$246.77	$246.75	$246.80
Purchase #6	$228.60	3.139%	$235.7758	$235.78	$235.80	$235.80
Purchase #7	$141.32	8.174%	$152.8715	$152.87	$152.85	$152.90
7 purchase totals =	$907.86		$963.9337	$963.94	$963.90	$964.10