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	$132.64	6.751%	$141.5945	$141.59	$141.60	$141.60
Purchase #2	$54.61	4.338%	$56.979	$56.98	$57.00	$57.00
Purchase #3	$204.95	6.622%	$218.5218	$218.52	$218.50	$218.50
Purchase #4	$141.62	6.239%	$150.4557	$150.46	$150.45	$150.50
Purchase #5	$18.40	5.687%	$19.4464	$19.45	$19.45	$19.40
Purchase #6	$64.51	4.718%	$67.5536	$67.55	$67.55	$67.60
Purchase #7	$77.53	7.674%	$83.4797	$83.48	$83.50	$83.50
7 purchase totals =	$694.26		$738.0307	$738.03	$738.05	$738.10