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	$53.25	8.818%	$57.9456	$57.95	$57.95	$57.90
Purchase #2	$35.88	12.773%	$40.463	$40.46	$40.45	$40.50
Purchase #3	$126.60	10.582%	$139.9968	$140.00	$140.00	$140.00
Purchase #4	$100.58	3.118%	$103.7161	$103.72	$103.70	$103.70
Purchase #5	$233.97	9.597%	$256.4241	$256.42	$256.40	$256.40
Purchase #6	$23.56	12.488%	$26.5022	$26.50	$26.50	$26.50
Purchase #7	$20.93	12.725%	$23.5933	$23.59	$23.60	$23.60
7 purchase totals =	$594.77		$648.6411	$648.64	$648.60	$648.60