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	$180.32	8.354%	$195.3839	$195.38	$195.40	$195.40
Purchase #2	$78.93	11.820%	$88.2595	$88.26	$88.25	$88.30
Purchase #3	$152.91	7.636%	$164.5862	$164.59	$164.60	$164.60
Purchase #4	$92.64	11.833%	$103.6021	$103.60	$103.60	$103.60
Purchase #5	$66.34	12.250%	$74.4667	$74.47	$74.45	$74.50
Purchase #6	$66.92	11.819%	$74.8293	$74.83	$74.85	$74.80
Purchase #7	$74.32	4.243%	$77.4734	$77.47	$77.45	$77.50
7 purchase totals =	$712.38		$778.6011	$778.60	$778.60	$778.70