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	$208.25	3.261%	$215.041	$215.04	$215.05	$215.00
Purchase #2	$157.54	6.227%	$167.35	$167.35	$167.35	$167.40
Purchase #3	$54.85	9.267%	$59.9329	$59.93	$59.95	$59.90
Purchase #4	$158.47	12.631%	$178.4863	$178.49	$178.50	$178.50
Purchase #5	$243.55	6.641%	$259.7242	$259.72	$259.70	$259.70
Purchase #6	$16.71	6.258%	$17.7557	$17.76	$17.75	$17.80
Purchase #7	$72.91	13.851%	$83.0088	$83.01	$83.00	$83.00
7 purchase totals =	$912.28		$981.2989	$981.30	$981.30	$981.30