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	$176.38	11.276%	$196.2686	$196.27	$196.25	$196.30
Purchase #2	$225.88	5.116%	$237.436	$237.44	$237.45	$237.40
Purchase #3	$7.74	5.818%	$8.1903	$8.19	$8.20	$8.20
Purchase #4	$158.67	12.261%	$178.1245	$178.12	$178.10	$178.10
Purchase #5	$69.39	12.575%	$78.1158	$78.12	$78.10	$78.10
Purchase #6	$89.67	12.492%	$100.8716	$100.87	$100.85	$100.90
Purchase #7	$6.39	8.758%	$6.9496	$6.95	$6.95	$6.90
7 purchase totals =	$734.12		$805.9564	$805.96	$805.90	$805.90