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	$71.87	9.845%	$78.9456	$78.95	$78.95	$78.90
Purchase #2	$12.38	8.584%	$13.4427	$13.44	$13.45	$13.40
Purchase #3	$17.52	9.548%	$19.1928	$19.19	$19.20	$19.20
Purchase #4	$213.88	13.580%	$242.9249	$242.92	$242.90	$242.90
Purchase #5	$100.25	12.139%	$112.4193	$112.42	$112.40	$112.40
Purchase #6	$135.29	11.360%	$150.6589	$150.66	$150.65	$150.70
Purchase #7	$158.55	10.264%	$174.8236	$174.82	$174.80	$174.80
7 purchase totals =	$709.74		$792.4078	$792.40	$792.35	$792.30