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	$185.86	7.141%	$199.1323	$199.13	$199.15	$199.10
Purchase #2	$178.31	3.742%	$184.9824	$184.98	$185.00	$185.00
Purchase #3	$121.88	8.220%	$131.8985	$131.90	$131.90	$131.90
Purchase #4	$20.58	12.584%	$23.1698	$23.17	$23.15	$23.20
Purchase #5	$78.61	4.636%	$82.2544	$82.25	$82.25	$82.30
Purchase #6	$24.72	11.121%	$27.4691	$27.47	$27.45	$27.50
Purchase #7	$35.90	6.413%	$38.2023	$38.20	$38.20	$38.20
7 purchase totals =	$645.86		$687.1088	$687.10	$687.10	$687.20