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	$144.76	7.450%	$155.5446	$155.54	$155.55	$155.50
Purchase #2	$132.53	5.568%	$139.9093	$139.91	$139.90	$139.90
Purchase #3	$211.93	10.267%	$233.6889	$233.69	$233.70	$233.70
Purchase #4	$172.90	11.502%	$192.787	$192.79	$192.80	$192.80
Purchase #5	$116.89	12.138%	$131.0781	$131.08	$131.10	$131.10
Purchase #6	$163.45	9.307%	$178.6623	$178.66	$178.65	$178.70
Purchase #7	$100.86	11.628%	$112.588	$112.59	$112.60	$112.60
7 purchase totals =	$1,043.32		$1,144.2582	$1,144.26	$1,144.30	$1,144.30