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	$175.68	11.796%	$196.4032	$196.40	$196.40	$196.40
Purchase #2	$174.38	3.390%	$180.2915	$180.29	$180.30	$180.30
Purchase #3	$157.86	8.620%	$171.4675	$171.47	$171.45	$171.50
Purchase #4	$34.94	8.801%	$38.0151	$38.02	$38.00	$38.00
Purchase #5	$133.45	12.540%	$150.1846	$150.18	$150.20	$150.20
Purchase #6	$61.74	6.106%	$65.5098	$65.51	$65.50	$65.50
Purchase #7	$50.97	12.222%	$57.1996	$57.20	$57.20	$57.20
7 purchase totals =	$789.02		$859.0713	$859.07	$859.05	$859.10