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	$171.29	8.697%	$186.1871	$186.19	$186.20	$186.20
Purchase #2	$215.40	3.296%	$222.4996	$222.50	$222.50	$222.50
Purchase #3	$52.78	5.390%	$55.6248	$55.62	$55.60	$55.60
Purchase #4	$131.30	7.840%	$141.5939	$141.59	$141.60	$141.60
Purchase #5	$201.56	9.241%	$220.1862	$220.19	$220.20	$220.20
Purchase #6	$41.45	6.300%	$44.0614	$44.06	$44.05	$44.10
Purchase #7	$167.89	13.218%	$190.0817	$190.08	$190.10	$190.10
7 purchase totals =	$981.67		$1,060.2347	$1,060.23	$1,060.25	$1,060.30