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	$143.56	6.648%	$153.1039	$153.10	$153.10	$153.10
Purchase #2	$165.69	4.595%	$173.3035	$173.30	$173.30	$173.30
Purchase #3	$105.88	8.179%	$114.5399	$114.54	$114.55	$114.50
Purchase #4	$133.46	6.405%	$142.0081	$142.01	$142.00	$142.00
Purchase #5	$217.35	5.773%	$229.8976	$229.90	$229.90	$229.90
Purchase #6	$164.94	10.676%	$182.549	$182.55	$182.55	$182.50
Purchase #7	$141.49	13.295%	$160.3011	$160.30	$160.30	$160.30
7 purchase totals =	$1,072.37		$1,155.7031	$1,155.70	$1,155.70	$1,155.60