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	$242.64	5.802%	$256.718	$256.72	$256.70	$256.70
Purchase #2	$38.88	13.567%	$44.1548	$44.15	$44.15	$44.20
Purchase #3	$90.98	4.607%	$95.1714	$95.17	$95.15	$95.20
Purchase #4	$138.60	7.406%	$148.8647	$148.86	$148.85	$148.90
Purchase #5	$42.54	3.277%	$43.934	$43.93	$43.95	$43.90
Purchase #6	$183.67	6.295%	$195.232	$195.23	$195.25	$195.20
Purchase #7	$178.69	8.755%	$194.3343	$194.33	$194.35	$194.30
7 purchase totals =	$916.00		$978.4092	$978.39	$978.40	$978.40