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	$133.72	10.599%	$147.893	$147.89	$147.90	$147.90
Purchase #2	$97.52	11.598%	$108.8304	$108.83	$108.85	$108.80
Purchase #3	$176.72	13.781%	$201.0738	$201.07	$201.05	$201.10
Purchase #4	$138.54	11.821%	$154.9168	$154.92	$154.90	$154.90
Purchase #5	$215.45	3.857%	$223.7599	$223.76	$223.75	$223.80
Purchase #6	$52.71	13.223%	$59.6798	$59.68	$59.70	$59.70
Purchase #7	$145.48	3.523%	$150.6053	$150.61	$150.60	$150.60
7 purchase totals =	$960.14		$1,046.7590	$1,046.76	$1,046.75	$1,046.80