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	$29.65	11.864%	$33.1677	$33.17	$33.15	$33.20
Purchase #2	$47.72	9.855%	$52.4228	$52.42	$52.40	$52.40
Purchase #3	$179.77	3.268%	$185.6449	$185.64	$185.65	$185.60
Purchase #4	$249.89	5.188%	$262.8543	$262.85	$262.85	$262.90
Purchase #5	$225.29	10.725%	$249.4524	$249.45	$249.45	$249.50
Purchase #6	$196.38	8.365%	$212.8072	$212.81	$212.80	$212.80
Purchase #7	$167.55	4.541%	$175.1584	$175.16	$175.15	$175.20
7 purchase totals =	$1,096.25		$1,171.5077	$1,171.50	$1,171.45	$1,171.60