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	$191.68	3.665%	$198.7051	$198.71	$198.70	$198.70
Purchase #2	$187.87	4.695%	$196.6905	$196.69	$196.70	$196.70
Purchase #3	$226.52	12.802%	$255.5191	$255.52	$255.50	$255.50
Purchase #4	$137.59	11.108%	$152.8735	$152.87	$152.85	$152.90
Purchase #5	$137.42	13.366%	$155.7876	$155.79	$155.80	$155.80
Purchase #6	$90.75	13.382%	$102.8942	$102.89	$102.90	$102.90
Purchase #7	$230.42	11.847%	$257.7179	$257.72	$257.70	$257.70
7 purchase totals =	$1,202.25		$1,320.1879	$1,320.19	$1,320.15	$1,320.20