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	$153.61	9.294%	$167.8865	$167.89	$167.90	$167.90
Purchase #2	$130.38	8.611%	$141.607	$141.61	$141.60	$141.60
Purchase #3	$66.93	3.795%	$69.47	$69.47	$69.45	$69.50
Purchase #4	$84.37	5.789%	$89.2542	$89.25	$89.25	$89.30
Purchase #5	$149.49	4.322%	$155.951	$155.95	$155.95	$156.00
Purchase #6	$103.34	7.712%	$111.3096	$111.31	$111.30	$111.30
Purchase #7	$113.64	4.254%	$118.4742	$118.47	$118.45	$118.50
7 purchase totals =	$801.76		$853.9525	$853.95	$853.90	$854.10