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	$230.90	11.522%	$257.5043	$257.50	$257.50	$257.50
Purchase #2	$34.56	9.612%	$37.8819	$37.88	$37.90	$37.90
Purchase #3	$61.47	3.770%	$63.7874	$63.79	$63.80	$63.80
Purchase #4	$109.41	13.459%	$124.1355	$124.14	$124.15	$124.10
Purchase #5	$196.38	4.166%	$204.5612	$204.56	$204.55	$204.60
Purchase #6	$170.34	3.670%	$176.5915	$176.59	$176.60	$176.60
Purchase #7	$142.33	8.808%	$154.8664	$154.87	$154.85	$154.90
7 purchase totals =	$945.39		$1,019.3282	$1,019.33	$1,019.35	$1,019.40