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	$229.46	8.684%	$249.3863	$249.39	$249.40	$249.40
Purchase #2	$200.55	5.495%	$211.5702	$211.57	$211.55	$211.60
Purchase #3	$103.54	5.510%	$109.2451	$109.25	$109.25	$109.20
Purchase #4	$100.97	3.782%	$104.7887	$104.79	$104.80	$104.80
Purchase #5	$187.65	12.137%	$210.4251	$210.43	$210.45	$210.40
Purchase #6	$231.40	3.543%	$239.5985	$239.60	$239.60	$239.60
Purchase #7	$40.46	8.563%	$43.9246	$43.92	$43.90	$43.90
7 purchase totals =	$1,094.03		$1,168.9385	$1,168.95	$1,168.95	$1,168.90