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	$167.59	12.801%	$189.0432	$189.04	$189.05	$189.00
Purchase #2	$184.56	10.508%	$203.9536	$203.95	$203.95	$204.00
Purchase #3	$18.31	13.742%	$20.8262	$20.83	$20.85	$20.80
Purchase #4	$199.28	13.453%	$226.0891	$226.09	$226.10	$226.10
Purchase #5	$57.97	9.575%	$63.5206	$63.52	$63.50	$63.50
Purchase #6	$216.78	7.866%	$233.8319	$233.83	$233.85	$233.80
Purchase #7	$62.76	6.294%	$66.7101	$66.71	$66.70	$66.70
7 purchase totals =	$907.25		$1,003.9747	$1,003.97	$1,004.00	$1,003.90