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	$233.96	8.221%	$253.1939	$253.19	$253.20	$253.20
Purchase #2	$245.99	4.273%	$256.5012	$256.50	$256.50	$256.50
Purchase #3	$150.64	5.349%	$158.6977	$158.70	$158.70	$158.70
Purchase #4	$92.49	7.833%	$99.7347	$99.73	$99.75	$99.70
Purchase #5	$134.71	5.657%	$142.3305	$142.33	$142.35	$142.30
Purchase #6	$62.49	8.142%	$67.5779	$67.58	$67.60	$67.60
Purchase #7	$56.43	11.172%	$62.7344	$62.73	$62.75	$62.70
7 purchase totals =	$976.71		$1,040.7703	$1,040.76	$1,040.85	$1,040.70