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	$58.97	13.784%	$67.0984	$67.10	$67.10	$67.10
Purchase #2	$178.60	6.636%	$190.4519	$190.45	$190.45	$190.50
Purchase #3	$137.41	9.520%	$150.4914	$150.49	$150.50	$150.50
Purchase #4	$58.78	11.644%	$65.6243	$65.62	$65.60	$65.60
Purchase #5	$57.66	3.817%	$59.8609	$59.86	$59.85	$59.90
Purchase #6	$220.51	4.867%	$231.2422	$231.24	$231.25	$231.20
Purchase #7	$147.62	8.847%	$160.6799	$160.68	$160.70	$160.70
7 purchase totals =	$859.55		$925.4490	$925.44	$925.45	$925.50