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	$11.45	9.360%	$12.5217	$12.52	$12.50	$12.50
Purchase #2	$88.28	5.874%	$93.4656	$93.47	$93.45	$93.50
Purchase #3	$50.76	5.716%	$53.6614	$53.66	$53.65	$53.70
Purchase #4	$168.67	9.753%	$185.1204	$185.12	$185.10	$185.10
Purchase #5	$184.85	12.797%	$208.5053	$208.51	$208.50	$208.50
Purchase #6	$224.77	13.817%	$255.8265	$255.83	$255.85	$255.80
Purchase #7	$236.62	13.843%	$269.3753	$269.38	$269.40	$269.40
7 purchase totals =	$965.40		$1,078.4762	$1,078.49	$1,078.45	$1,078.50