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	$218.94	4.568%	$228.9412	$228.94	$228.95	$228.90
Purchase #2	$174.31	9.105%	$190.1809	$190.18	$190.20	$190.20
Purchase #3	$241.89	12.579%	$272.3173	$272.32	$272.30	$272.30
Purchase #4	$146.90	12.434%	$165.1655	$165.17	$165.15	$165.20
Purchase #5	$39.44	9.346%	$43.1261	$43.13	$43.15	$43.10
Purchase #6	$91.42	10.427%	$100.9524	$100.95	$100.95	$101.00
Purchase #7	$42.30	5.535%	$44.6413	$44.64	$44.65	$44.60
7 purchase totals =	$955.20		$1,045.3247	$1,045.33	$1,045.35	$1,045.30