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	$114.35	7.578%	$123.0154	$123.02	$123.00	$123.00
Purchase #2	$179.59	3.606%	$186.066	$186.07	$186.05	$186.10
Purchase #3	$74.37	11.475%	$82.904	$82.90	$82.90	$82.90
Purchase #4	$158.99	5.282%	$167.3879	$167.39	$167.40	$167.40
Purchase #5	$19.81	13.218%	$22.4285	$22.43	$22.45	$22.40
Purchase #6	$231.33	6.427%	$246.1976	$246.20	$246.20	$246.20
Purchase #7	$246.46	5.287%	$259.4903	$259.49	$259.50	$259.50
7 purchase totals =	$1,024.90		$1,087.4897	$1,087.50	$1,087.50	$1,087.50