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	$179.47	4.506%	$187.5569	$187.56	$187.55	$187.60
Purchase #2	$60.49	5.770%	$63.9803	$63.98	$64.00	$64.00
Purchase #3	$166.95	7.370%	$179.2542	$179.25	$179.25	$179.30
Purchase #4	$142.56	5.538%	$150.455	$150.46	$150.45	$150.50
Purchase #5	$38.44	5.671%	$40.6199	$40.62	$40.60	$40.60
Purchase #6	$192.81	6.281%	$204.9204	$204.92	$204.90	$204.90
Purchase #7	$167.91	8.647%	$182.4292	$182.43	$182.45	$182.40
7 purchase totals =	$948.63		$1,009.2159	$1,009.22	$1,009.20	$1,009.30