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	$164.71	8.228%	$178.2623	$178.26	$178.25	$178.30
Purchase #2	$131.45	4.663%	$137.5795	$137.58	$137.60	$137.60
Purchase #3	$139.46	4.244%	$145.3787	$145.38	$145.40	$145.40
Purchase #4	$247.38	13.853%	$281.6496	$281.65	$281.65	$281.60
Purchase #5	$101.54	13.703%	$115.454	$115.45	$115.45	$115.50
Purchase #6	$167.96	7.488%	$180.5368	$180.54	$180.55	$180.50
Purchase #7	$33.64	12.131%	$37.7209	$37.72	$37.70	$37.70
7 purchase totals =	$986.14		$1,076.5818	$1,076.58	$1,076.60	$1,076.60