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	$81.34	13.744%	$92.5194	$92.52	$92.50	$92.50
Purchase #2	$92.54	11.276%	$102.9748	$102.97	$102.95	$103.00
Purchase #3	$152.26	12.524%	$171.329	$171.33	$171.35	$171.30
Purchase #4	$180.92	10.224%	$199.4173	$199.42	$199.40	$199.40
Purchase #5	$225.27	13.469%	$255.6116	$255.61	$255.60	$255.60
Purchase #6	$180.90	6.868%	$193.3242	$193.32	$193.30	$193.30
Purchase #7	$134.35	12.318%	$150.8992	$150.90	$150.90	$150.90
7 purchase totals =	$1,047.58		$1,166.0755	$1,166.07	$1,166.00	$1,166.00