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	$205.75	9.362%	$225.0123	$225.01	$225.00	$225.00
Purchase #2	$51.74	13.139%	$58.5381	$58.54	$58.55	$58.50
Purchase #3	$246.66	3.736%	$255.8752	$255.88	$255.90	$255.90
Purchase #4	$13.84	4.400%	$14.449	$14.45	$14.45	$14.40
Purchase #5	$179.46	5.532%	$189.3877	$189.39	$189.40	$189.40
Purchase #6	$141.77	11.696%	$158.3514	$158.35	$158.35	$158.40
Purchase #7	$238.35	11.721%	$266.287	$266.29	$266.30	$266.30
7 purchase totals =	$1,077.57		$1,167.9007	$1,167.91	$1,167.95	$1,167.90