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	$145.64	7.162%	$156.0707	$156.07	$156.05	$156.10
Purchase #2	$157.28	7.374%	$168.8778	$168.88	$168.90	$168.90
Purchase #3	$132.67	7.874%	$143.1164	$143.12	$143.10	$143.10
Purchase #4	$53.91	11.169%	$59.9312	$59.93	$59.95	$59.90
Purchase #5	$80.89	3.279%	$83.5424	$83.54	$83.55	$83.50
Purchase #6	$110.91	8.715%	$120.5758	$120.58	$120.60	$120.60
Purchase #7	$168.84	4.697%	$176.7704	$176.77	$176.75	$176.80
7 purchase totals =	$850.14		$908.8847	$908.89	$908.90	$908.90