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	$184.32	7.654%	$198.4279	$198.43	$198.45	$198.40
Purchase #2	$162.64	4.127%	$169.3522	$169.35	$169.35	$169.40
Purchase #3	$34.88	4.668%	$36.5082	$36.51	$36.50	$36.50
Purchase #4	$82.58	7.857%	$89.0683	$89.07	$89.05	$89.10
Purchase #5	$136.78	13.767%	$155.6105	$155.61	$155.60	$155.60
Purchase #6	$32.62	13.407%	$36.9934	$36.99	$37.00	$37.00
Purchase #7	$144.86	8.316%	$156.9066	$156.91	$156.90	$156.90
7 purchase totals =	$778.68		$842.8671	$842.87	$842.85	$842.90