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	$119.38	3.228%	$123.2336	$123.23	$123.25	$123.20
Purchase #2	$90.65	10.669%	$100.3214	$100.32	$100.30	$100.30
Purchase #3	$75.84	6.316%	$80.6301	$80.63	$80.65	$80.60
Purchase #4	$91.37	4.227%	$95.2322	$95.23	$95.25	$95.20
Purchase #5	$151.52	10.538%	$167.4872	$167.49	$167.50	$167.50
Purchase #6	$21.26	7.788%	$22.9157	$22.92	$22.90	$22.90
Purchase #7	$105.48	13.854%	$120.0932	$120.09	$120.10	$120.10
7 purchase totals =	$655.50		$709.9134	$709.91	$709.95	$709.80