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	$119.34	3.215%	$123.1768	$123.18	$123.20	$123.20
Purchase #2	$50.32	3.483%	$52.0726	$52.07	$52.05	$52.10
Purchase #3	$182.88	7.163%	$195.9797	$195.98	$196.00	$196.00
Purchase #4	$68.96	7.105%	$73.8596	$73.86	$73.85	$73.90
Purchase #5	$149.88	12.522%	$168.648	$168.65	$168.65	$168.60
Purchase #6	$39.91	10.587%	$44.1353	$44.14	$44.15	$44.10
Purchase #7	$56.27	11.170%	$62.5554	$62.56	$62.55	$62.60
7 purchase totals =	$667.56		$720.4274	$720.44	$720.45	$720.50