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	$242.63	13.725%	$275.931	$275.93	$275.95	$275.90
Purchase #2	$34.88	8.690%	$37.9111	$37.91	$37.90	$37.90
Purchase #3	$74.28	10.684%	$82.2161	$82.22	$82.20	$82.20
Purchase #4	$145.47	9.141%	$158.7674	$158.77	$158.75	$158.80
Purchase #5	$245.92	11.811%	$274.9656	$274.97	$274.95	$275.00
Purchase #6	$72.59	6.215%	$77.1015	$77.10	$77.10	$77.10
Purchase #7	$155.85	4.560%	$162.9568	$162.96	$162.95	$163.00
7 purchase totals =	$971.62		$1,069.8495	$1,069.86	$1,069.80	$1,069.90