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	$89.49	11.554%	$99.8297	$99.83	$99.85	$99.80
Purchase #2	$241.92	8.150%	$261.6365	$261.64	$261.65	$261.60
Purchase #3	$134.33	10.238%	$148.0827	$148.08	$148.10	$148.10
Purchase #4	$81.67	8.735%	$88.8039	$88.80	$88.80	$88.80
Purchase #5	$86.25	9.259%	$94.2359	$94.24	$94.25	$94.20
Purchase #6	$98.82	13.229%	$111.8929	$111.89	$111.90	$111.90
Purchase #7	$180.47	13.641%	$205.0879	$205.09	$205.10	$205.10
7 purchase totals =	$912.95		$1,009.5695	$1,009.57	$1,009.65	$1,009.50