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	$99.39	6.441%	$105.7917	$105.79	$105.80	$105.80
Purchase #2	$187.77	12.314%	$210.892	$210.89	$210.90	$210.90
Purchase #3	$87.36	11.337%	$97.264	$97.26	$97.25	$97.30
Purchase #4	$27.41	5.382%	$28.8852	$28.89	$28.90	$28.90
Purchase #5	$194.68	5.725%	$205.8254	$205.83	$205.85	$205.80
Purchase #6	$177.83	11.482%	$198.2484	$198.25	$198.25	$198.20
Purchase #7	$248.47	9.438%	$271.9206	$271.92	$271.90	$271.90
7 purchase totals =	$1,022.91		$1,118.8273	$1,118.83	$1,118.85	$1,118.80