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	$102.85	5.706%	$108.7186	$108.72	$108.70	$108.70
Purchase #2	$72.98	10.216%	$80.4356	$80.44	$80.45	$80.40
Purchase #3	$33.38	12.218%	$37.4584	$37.46	$37.45	$37.50
Purchase #4	$100.95	11.600%	$112.6602	$112.66	$112.65	$112.70
Purchase #5	$100.27	8.404%	$108.6967	$108.70	$108.70	$108.70
Purchase #6	$57.75	3.503%	$59.773	$59.77	$59.75	$59.80
Purchase #7	$53.43	10.219%	$58.89	$58.89	$58.90	$58.90
7 purchase totals =	$521.61		$566.6325	$566.64	$566.60	$566.70