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	$151.98	8.773%	$165.3132	$165.31	$165.30	$165.30
Purchase #2	$190.89	10.408%	$210.7578	$210.76	$210.75	$210.80
Purchase #3	$24.77	9.311%	$27.0763	$27.08	$27.10	$27.10
Purchase #4	$75.33	4.150%	$78.4562	$78.46	$78.45	$78.50
Purchase #5	$103.58	7.745%	$111.6023	$111.60	$111.60	$111.60
Purchase #6	$119.52	4.814%	$125.2737	$125.27	$125.25	$125.30
Purchase #7	$61.34	12.408%	$68.9511	$68.95	$68.95	$69.00
7 purchase totals =	$727.41		$787.4306	$787.43	$787.40	$787.60