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	$95.43	4.551%	$99.773	$99.77	$99.75	$99.80
Purchase #2	$42.30	6.137%	$44.896	$44.90	$44.90	$44.90
Purchase #3	$241.74	13.349%	$274.0099	$274.01	$274.00	$274.00
Purchase #4	$148.70	6.751%	$158.7387	$158.74	$158.75	$158.70
Purchase #5	$122.42	4.383%	$127.7857	$127.79	$127.80	$127.80
Purchase #6	$68.88	10.438%	$76.0697	$76.07	$76.05	$76.10
Purchase #7	$63.57	6.579%	$67.7523	$67.75	$67.75	$67.80
7 purchase totals =	$783.04		$849.0253	$849.03	$849.00	$849.10