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	$114.57	8.577%	$124.3967	$124.40	$124.40	$124.40
Purchase #2	$128.43	3.595%	$133.0471	$133.05	$133.05	$133.00
Purchase #3	$38.42	5.429%	$40.5058	$40.51	$40.50	$40.50
Purchase #4	$129.27	13.341%	$146.5159	$146.52	$146.50	$146.50
Purchase #5	$136.83	8.204%	$148.0555	$148.06	$148.05	$148.10
Purchase #6	$50.30	11.769%	$56.2198	$56.22	$56.20	$56.20
Purchase #7	$55.46	6.758%	$59.208	$59.21	$59.20	$59.20
7 purchase totals =	$653.28		$707.9488	$707.97	$707.90	$707.90