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	$82.69	9.632%	$90.6547	$90.65	$90.65	$90.70
Purchase #2	$187.77	4.387%	$196.0075	$196.01	$196.00	$196.00
Purchase #3	$71.44	13.505%	$81.088	$81.09	$81.10	$81.10
Purchase #4	$20.66	7.418%	$22.1926	$22.19	$22.20	$22.20
Purchase #5	$40.80	13.293%	$46.2235	$46.22	$46.20	$46.20
Purchase #6	$114.91	7.600%	$123.6432	$123.64	$123.65	$123.60
Purchase #7	$96.26	11.493%	$107.3232	$107.32	$107.30	$107.30
7 purchase totals =	$614.53		$667.1327	$667.12	$667.10	$667.10