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	$59.73	9.831%	$65.6021	$65.60	$65.60	$65.60
Purchase #2	$54.51	9.114%	$59.478	$59.48	$59.50	$59.50
Purchase #3	$93.40	12.324%	$104.9106	$104.91	$104.90	$104.90
Purchase #4	$180.52	13.489%	$204.8703	$204.87	$204.85	$204.90
Purchase #5	$133.27	7.111%	$142.7468	$142.75	$142.75	$142.70
Purchase #6	$130.66	11.237%	$145.3423	$145.34	$145.35	$145.30
Purchase #7	$29.82	6.659%	$31.8057	$31.81	$31.80	$31.80
7 purchase totals =	$681.91		$754.7558	$754.76	$754.75	$754.70