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	$144.98	12.596%	$163.2417	$163.24	$163.25	$163.20
Purchase #2	$88.40	13.383%	$100.2306	$100.23	$100.25	$100.20
Purchase #3	$228.52	9.475%	$250.1723	$250.17	$250.15	$250.20
Purchase #4	$29.78	10.440%	$32.889	$32.89	$32.90	$32.90
Purchase #5	$91.33	4.114%	$95.0873	$95.09	$95.10	$95.10
Purchase #6	$87.52	4.867%	$91.7796	$91.78	$91.80	$91.80
Purchase #7	$27.85	3.757%	$28.8963	$28.90	$28.90	$28.90
7 purchase totals =	$698.38		$762.2968	$762.30	$762.35	$762.30