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	$181.30	6.617%	$193.2966	$193.30	$193.30	$193.30
Purchase #2	$77.84	7.834%	$83.938	$83.94	$83.95	$83.90
Purchase #3	$83.84	8.349%	$90.8398	$90.84	$90.85	$90.80
Purchase #4	$54.56	11.690%	$60.9381	$60.94	$60.95	$60.90
Purchase #5	$93.69	6.830%	$100.089	$100.09	$100.10	$100.10
Purchase #6	$202.73	12.301%	$227.6678	$227.67	$227.65	$227.70
Purchase #7	$241.27	6.358%	$256.6099	$256.61	$256.60	$256.60
7 purchase totals =	$935.23		$1,013.3792	$1,013.39	$1,013.40	$1,013.30