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	$71.62	7.685%	$77.124	$77.12	$77.10	$77.10
Purchase #2	$199.55	7.589%	$214.6938	$214.69	$214.70	$214.70
Purchase #3	$176.56	13.493%	$200.3832	$200.38	$200.40	$200.40
Purchase #4	$119.70	11.854%	$133.8892	$133.89	$133.90	$133.90
Purchase #5	$164.39	4.205%	$171.3026	$171.30	$171.30	$171.30
Purchase #6	$26.62	11.404%	$29.6557	$29.66	$29.65	$29.70
Purchase #7	$164.65	10.448%	$181.8526	$181.85	$181.85	$181.90
7 purchase totals =	$923.09		$1,008.9011	$1,008.89	$1,008.90	$1,009.00