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	$58.48	6.185%	$62.097	$62.10	$62.10	$62.10
Purchase #2	$244.29	13.833%	$278.0826	$278.08	$278.10	$278.10
Purchase #3	$76.40	8.149%	$82.6258	$82.63	$82.65	$82.60
Purchase #4	$198.71	9.157%	$216.9059	$216.91	$216.90	$216.90
Purchase #5	$145.67	6.641%	$155.3439	$155.34	$155.35	$155.30
Purchase #6	$206.98	6.278%	$219.9742	$219.97	$219.95	$220.00
Purchase #7	$103.48	7.705%	$111.4531	$111.45	$111.45	$111.50
7 purchase totals =	$1,034.01		$1,126.4825	$1,126.48	$1,126.50	$1,126.50