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	$102.27	3.440%	$105.7881	$105.79	$105.80	$105.80
Purchase #2	$71.45	5.646%	$75.4841	$75.48	$75.50	$75.50
Purchase #3	$87.38	9.628%	$95.7929	$95.79	$95.80	$95.80
Purchase #4	$54.55	12.502%	$61.3698	$61.37	$61.35	$61.40
Purchase #5	$225.53	3.377%	$233.1461	$233.15	$233.15	$233.10
Purchase #6	$74.28	5.671%	$78.4924	$78.49	$78.50	$78.50
Purchase #7	$12.25	12.689%	$13.8044	$13.80	$13.80	$13.80
7 purchase totals =	$627.71		$663.8778	$663.87	$663.90	$663.90