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	$169.51	13.359%	$192.1548	$192.15	$192.15	$192.20
Purchase #2	$14.82	3.693%	$15.3673	$15.37	$15.35	$15.40
Purchase #3	$59.48	13.337%	$67.4128	$67.41	$67.40	$67.40
Purchase #4	$11.41	12.584%	$12.8458	$12.85	$12.85	$12.80
Purchase #5	$197.72	13.135%	$223.6905	$223.69	$223.70	$223.70
Purchase #6	$81.81	4.818%	$85.7516	$85.75	$85.75	$85.80
Purchase #7	$184.37	3.534%	$190.8856	$190.89	$190.90	$190.90
7 purchase totals =	$719.12		$788.1084	$788.11	$788.10	$788.20