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	$76.76	13.150%	$86.8539	$86.85	$86.85	$86.90
Purchase #2	$102.92	9.122%	$112.3084	$112.31	$112.30	$112.30
Purchase #3	$36.55	3.779%	$37.9312	$37.93	$37.95	$37.90
Purchase #4	$107.39	12.135%	$120.4218	$120.42	$120.40	$120.40
Purchase #5	$153.32	9.446%	$167.8026	$167.80	$167.80	$167.80
Purchase #6	$83.83	7.643%	$90.2371	$90.24	$90.25	$90.20
Purchase #7	$155.90	7.471%	$167.5473	$167.55	$167.55	$167.50
7 purchase totals =	$716.67		$783.1023	$783.10	$783.10	$783.00