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	$205.71	4.789%	$215.5615	$215.56	$215.55	$215.60
Purchase #2	$87.53	11.560%	$97.6485	$97.65	$97.65	$97.60
Purchase #3	$43.58	3.688%	$45.1872	$45.19	$45.20	$45.20
Purchase #4	$104.25	7.286%	$111.8457	$111.85	$111.85	$111.80
Purchase #5	$31.86	7.696%	$34.3119	$34.31	$34.30	$34.30
Purchase #6	$148.89	12.500%	$167.5013	$167.50	$167.50	$167.50
Purchase #7	$130.57	11.258%	$145.2696	$145.27	$145.25	$145.30
7 purchase totals =	$752.39		$817.3257	$817.33	$817.30	$817.30