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	$10.31	6.149%	$10.944	$10.94	$10.95	$10.90
Purchase #2	$14.88	13.522%	$16.8921	$16.89	$16.90	$16.90
Purchase #3	$104.38	11.629%	$116.5184	$116.52	$116.50	$116.50
Purchase #4	$212.90	10.318%	$234.867	$234.87	$234.85	$234.90
Purchase #5	$249.54	10.401%	$275.4947	$275.49	$275.50	$275.50
Purchase #6	$41.78	3.658%	$43.3083	$43.31	$43.30	$43.30
Purchase #7	$186.31	3.414%	$192.6706	$192.67	$192.65	$192.70
7 purchase totals =	$820.10		$890.6951	$890.69	$890.65	$890.70