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	$153.41	5.518%	$161.8752	$161.88	$161.90	$161.90
Purchase #2	$30.62	4.190%	$31.903	$31.90	$31.90	$31.90
Purchase #3	$13.91	11.501%	$15.5098	$15.51	$15.50	$15.50
Purchase #4	$10.27	6.729%	$10.9611	$10.96	$10.95	$11.00
Purchase #5	$40.96	6.316%	$43.547	$43.55	$43.55	$43.50
Purchase #6	$196.90	12.111%	$220.7466	$220.75	$220.75	$220.70
Purchase #7	$250.43	9.210%	$273.4946	$273.49	$273.50	$273.50
7 purchase totals =	$696.50		$758.0373	$758.04	$758.05	$758.00