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	$246.78	6.500%	$262.8207	$262.82	$262.80	$262.80
Purchase #2	$38.43	13.227%	$43.5131	$43.51	$43.50	$43.50
Purchase #3	$185.44	13.522%	$210.5152	$210.52	$210.50	$210.50
Purchase #4	$196.29	3.531%	$203.221	$203.22	$203.20	$203.20
Purchase #5	$92.48	6.348%	$98.3506	$98.35	$98.35	$98.40
Purchase #6	$132.38	9.719%	$145.246	$145.25	$145.25	$145.20
Purchase #7	$53.55	7.672%	$57.6584	$57.66	$57.65	$57.70
7 purchase totals =	$945.35		$1,021.3250	$1,021.33	$1,021.25	$1,021.30