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	$51.27	10.415%	$56.6098	$56.61	$56.60	$56.60
Purchase #2	$95.52	8.280%	$103.4291	$103.43	$103.45	$103.40
Purchase #3	$224.29	13.665%	$254.9392	$254.94	$254.95	$254.90
Purchase #4	$65.46	6.139%	$69.4786	$69.48	$69.50	$69.50
Purchase #5	$243.37	6.655%	$259.5663	$259.57	$259.55	$259.60
Purchase #6	$65.84	9.545%	$72.1244	$72.12	$72.10	$72.10
Purchase #7	$117.87	5.675%	$124.5591	$124.56	$124.55	$124.60
7 purchase totals =	$863.62		$940.7065	$940.71	$940.70	$940.70