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	$62.43	4.486%	$65.2306	$65.23	$65.25	$65.20
Purchase #2	$183.76	9.254%	$200.7652	$200.77	$200.75	$200.80
Purchase #3	$159.99	13.556%	$181.6782	$181.68	$181.70	$181.70
Purchase #4	$200.54	11.772%	$224.1476	$224.15	$224.15	$224.10
Purchase #5	$181.63	10.348%	$200.4251	$200.43	$200.45	$200.40
Purchase #6	$106.61	11.554%	$118.9277	$118.93	$118.95	$118.90
Purchase #7	$145.60	9.584%	$159.5543	$159.55	$159.55	$159.60
7 purchase totals =	$1,040.56		$1,150.7287	$1,150.74	$1,150.80	$1,150.70