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	$176.40	3.814%	$183.1279	$183.13	$183.15	$183.10
Purchase #2	$56.84	4.204%	$59.2296	$59.23	$59.25	$59.20
Purchase #3	$242.38	11.305%	$269.7811	$269.78	$269.80	$269.80
Purchase #4	$206.90	8.853%	$225.2169	$225.22	$225.20	$225.20
Purchase #5	$46.68	13.362%	$52.9174	$52.92	$52.90	$52.90
Purchase #6	$12.72	4.738%	$13.3227	$13.32	$13.30	$13.30
Purchase #7	$82.81	5.453%	$87.3256	$87.33	$87.35	$87.30
7 purchase totals =	$824.73		$890.9212	$890.93	$890.95	$890.80