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	$152.95	13.716%	$173.9286	$173.93	$173.95	$173.90
Purchase #2	$127.34	11.688%	$142.2235	$142.22	$142.20	$142.20
Purchase #3	$58.49	8.703%	$63.5804	$63.58	$63.60	$63.60
Purchase #4	$45.77	9.381%	$50.0637	$50.06	$50.05	$50.10
Purchase #5	$50.94	6.758%	$54.3825	$54.38	$54.40	$54.40
Purchase #6	$159.75	3.850%	$165.9004	$165.90	$165.90	$165.90
Purchase #7	$197.31	13.784%	$224.5072	$224.51	$224.50	$224.50
7 purchase totals =	$792.55		$874.5863	$874.58	$874.60	$874.60