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	$32.74	5.207%	$34.4448	$34.44	$34.45	$34.40
Purchase #2	$103.41	7.747%	$111.4212	$111.42	$111.40	$111.40
Purchase #3	$66.27	7.725%	$71.3894	$71.39	$71.40	$71.40
Purchase #4	$249.49	8.432%	$270.527	$270.53	$270.55	$270.50
Purchase #5	$66.60	9.245%	$72.7572	$72.76	$72.75	$72.80
Purchase #6	$200.61	7.220%	$215.094	$215.09	$215.10	$215.10
Purchase #7	$179.78	11.611%	$200.6543	$200.65	$200.65	$200.70
7 purchase totals =	$898.90		$976.2879	$976.28	$976.30	$976.30