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	$45.85	5.541%	$48.3905	$48.39	$48.40	$48.40
Purchase #2	$176.47	5.304%	$185.83	$185.83	$185.85	$185.80
Purchase #3	$30.33	7.749%	$32.6803	$32.68	$32.70	$32.70
Purchase #4	$31.56	11.695%	$35.2509	$35.25	$35.25	$35.30
Purchase #5	$59.78	4.364%	$62.3888	$62.39	$62.40	$62.40
Purchase #6	$18.92	11.350%	$21.0674	$21.07	$21.05	$21.10
Purchase #7	$14.45	7.646%	$15.5548	$15.55	$15.55	$15.60
7 purchase totals =	$377.36		$401.1627	$401.16	$401.20	$401.30