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	$178.94	7.281%	$191.9686	$191.97	$191.95	$192.00
Purchase #2	$208.69	11.671%	$233.0462	$233.05	$233.05	$233.00
Purchase #3	$176.95	11.232%	$196.825	$196.83	$196.85	$196.80
Purchase #4	$77.70	13.180%	$87.9409	$87.94	$87.95	$87.90
Purchase #5	$135.90	5.824%	$143.8148	$143.81	$143.80	$143.80
Purchase #6	$168.65	3.536%	$174.6135	$174.61	$174.60	$174.60
Purchase #7	$41.32	4.807%	$43.3063	$43.31	$43.30	$43.30
7 purchase totals =	$988.15		$1,071.5153	$1,071.52	$1,071.50	$1,071.40