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	$188.72	13.644%	$214.469	$214.47	$214.45	$214.50
Purchase #2	$217.94	10.291%	$240.3682	$240.37	$240.35	$240.40
Purchase #3	$38.69	3.726%	$40.1316	$40.13	$40.15	$40.10
Purchase #4	$183.69	4.457%	$191.8771	$191.88	$191.90	$191.90
Purchase #5	$161.35	6.310%	$171.5312	$171.53	$171.55	$171.50
Purchase #6	$185.36	4.733%	$194.1331	$194.13	$194.15	$194.10
Purchase #7	$165.93	6.329%	$176.4317	$176.43	$176.45	$176.40
7 purchase totals =	$1,141.68		$1,228.9419	$1,228.94	$1,229.00	$1,228.90