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	$102.82	9.355%	$112.4388	$112.44	$112.45	$112.40
Purchase #2	$147.92	11.478%	$164.8983	$164.90	$164.90	$164.90
Purchase #3	$45.83	12.542%	$51.578	$51.58	$51.60	$51.60
Purchase #4	$196.76	10.472%	$217.3647	$217.36	$217.35	$217.40
Purchase #5	$133.86	12.263%	$150.2753	$150.28	$150.30	$150.30
Purchase #6	$97.39	11.457%	$108.548	$108.55	$108.55	$108.50
Purchase #7	$135.56	13.198%	$153.4512	$153.45	$153.45	$153.50
7 purchase totals =	$860.14		$958.5543	$958.56	$958.60	$958.60