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	$174.61	10.104%	$192.2526	$192.25	$192.25	$192.30
Purchase #2	$244.54	10.738%	$270.7987	$270.80	$270.80	$270.80
Purchase #3	$222.50	9.857%	$244.4318	$244.43	$244.45	$244.40
Purchase #4	$201.69	6.757%	$215.3182	$215.32	$215.30	$215.30
Purchase #5	$85.34	11.304%	$94.9868	$94.99	$95.00	$95.00
Purchase #6	$38.38	3.733%	$39.8127	$39.81	$39.80	$39.80
Purchase #7	$49.55	8.154%	$53.5903	$53.59	$53.60	$53.60
7 purchase totals =	$1,016.61		$1,111.1911	$1,111.19	$1,111.20	$1,111.20