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	$58.91	5.426%	$62.1065	$62.11	$62.10	$62.10
Purchase #2	$83.42	7.461%	$89.644	$89.64	$89.65	$89.60
Purchase #3	$196.38	13.758%	$223.398	$223.40	$223.40	$223.40
Purchase #4	$180.64	10.724%	$200.0118	$200.01	$200.00	$200.00
Purchase #5	$49.50	10.126%	$54.5124	$54.51	$54.50	$54.50
Purchase #6	$139.46	12.840%	$157.3667	$157.37	$157.35	$157.40
Purchase #7	$87.61	6.120%	$92.9717	$92.97	$92.95	$93.00
7 purchase totals =	$795.92		$880.0111	$880.01	$879.95	$880.00