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	$183.31	11.452%	$204.3027	$204.30	$204.30	$204.30
Purchase #2	$62.86	7.750%	$67.7317	$67.73	$67.75	$67.70
Purchase #3	$73.49	7.383%	$78.9158	$78.92	$78.90	$78.90
Purchase #4	$81.43	10.547%	$90.0184	$90.02	$90.00	$90.00
Purchase #5	$151.51	3.528%	$156.8553	$156.86	$156.85	$156.90
Purchase #6	$41.56	8.631%	$45.147	$45.15	$45.15	$45.10
Purchase #7	$208.27	12.647%	$234.6099	$234.61	$234.60	$234.60
7 purchase totals =	$802.43		$877.5808	$877.59	$877.55	$877.50