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	$187.33	9.493%	$205.1132	$205.11	$205.10	$205.10
Purchase #2	$194.47	5.573%	$205.3078	$205.31	$205.30	$205.30
Purchase #3	$187.58	11.244%	$208.6715	$208.67	$208.65	$208.70
Purchase #4	$103.56	12.513%	$116.5185	$116.52	$116.50	$116.50
Purchase #5	$59.69	7.345%	$64.0742	$64.07	$64.05	$64.10
Purchase #6	$112.77	5.803%	$119.314	$119.31	$119.30	$119.30
Purchase #7	$64.55	5.241%	$67.9331	$67.93	$67.95	$67.90
7 purchase totals =	$909.95		$986.9323	$986.92	$986.85	$986.90