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	$51.89	7.594%	$55.8305	$55.83	$55.85	$55.80
Purchase #2	$101.41	9.783%	$111.3309	$111.33	$111.35	$111.30
Purchase #3	$196.75	8.627%	$213.7236	$213.72	$213.70	$213.70
Purchase #4	$246.53	10.536%	$272.5044	$272.50	$272.50	$272.50
Purchase #5	$248.52	13.296%	$281.5632	$281.56	$281.55	$281.60
Purchase #6	$205.31	11.664%	$229.2574	$229.26	$229.25	$229.30
Purchase #7	$238.61	13.762%	$271.4475	$271.45	$271.45	$271.40
7 purchase totals =	$1,289.02		$1,435.6575	$1,435.65	$1,435.65	$1,435.60