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	$167.77	5.187%	$176.4722	$176.47	$176.45	$176.50
Purchase #2	$143.82	4.790%	$150.709	$150.71	$150.70	$150.70
Purchase #3	$165.25	5.281%	$173.9769	$173.98	$174.00	$174.00
Purchase #4	$163.61	11.217%	$181.9621	$181.96	$181.95	$182.00
Purchase #5	$78.66	13.246%	$89.0793	$89.08	$89.10	$89.10
Purchase #6	$158.58	6.228%	$168.4564	$168.46	$168.45	$168.50
Purchase #7	$217.68	13.773%	$247.6611	$247.66	$247.65	$247.70
7 purchase totals =	$1,095.37		$1,188.3170	$1,188.32	$1,188.30	$1,188.50