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	$126.82	12.557%	$142.7448	$142.74	$142.75	$142.70
Purchase #2	$38.77	11.568%	$43.2549	$43.25	$43.25	$43.30
Purchase #3	$117.71	7.558%	$126.6065	$126.61	$126.60	$126.60
Purchase #4	$220.93	5.817%	$233.7815	$233.78	$233.80	$233.80
Purchase #5	$95.52	8.399%	$103.5427	$103.54	$103.55	$103.50
Purchase #6	$202.54	7.344%	$217.4145	$217.41	$217.40	$217.40
Purchase #7	$105.41	7.149%	$112.9458	$112.95	$112.95	$112.90
7 purchase totals =	$907.70		$980.2907	$980.28	$980.30	$980.20