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	$118.43	6.461%	$126.0818	$126.08	$126.10	$126.10
Purchase #2	$116.95	12.176%	$131.1898	$131.19	$131.20	$131.20
Purchase #3	$45.98	12.373%	$51.6691	$51.67	$51.65	$51.70
Purchase #4	$127.94	11.452%	$142.5917	$142.59	$142.60	$142.60
Purchase #5	$60.54	10.693%	$67.0135	$67.01	$67.00	$67.00
Purchase #6	$167.70	7.196%	$179.7677	$179.77	$179.75	$179.80
Purchase #7	$204.69	11.678%	$228.5937	$228.59	$228.60	$228.60
7 purchase totals =	$842.23		$926.9073	$926.90	$926.90	$927.00