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	$131.53	4.802%	$137.8461	$137.85	$137.85	$137.80
Purchase #2	$229.83	5.230%	$241.8501	$241.85	$241.85	$241.90
Purchase #3	$236.75	4.491%	$247.3824	$247.38	$247.40	$247.40
Purchase #4	$248.59	4.462%	$259.6821	$259.68	$259.70	$259.70
Purchase #5	$77.70	7.701%	$83.6837	$83.68	$83.70	$83.70
Purchase #6	$185.48	5.861%	$196.351	$196.35	$196.35	$196.40
Purchase #7	$61.74	7.657%	$66.4674	$66.47	$66.45	$66.50
7 purchase totals =	$1,171.62		$1,233.2628	$1,233.26	$1,233.30	$1,233.40