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	$9.60	9.669%	$10.5282	$10.53	$10.55	$10.50
Purchase #2	$123.71	6.596%	$131.8699	$131.87	$131.85	$131.90
Purchase #3	$80.28	8.148%	$86.8212	$86.82	$86.80	$86.80
Purchase #4	$87.83	5.781%	$92.9075	$92.91	$92.90	$92.90
Purchase #5	$99.39	10.616%	$109.9412	$109.94	$109.95	$109.90
Purchase #6	$226.50	6.792%	$241.8839	$241.88	$241.90	$241.90
Purchase #7	$77.69	5.262%	$81.778	$81.78	$81.80	$81.80
7 purchase totals =	$705.00		$755.7299	$755.73	$755.75	$755.70