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	$195.86	11.151%	$217.7003	$217.70	$217.70	$217.70
Purchase #2	$51.53	7.338%	$55.3113	$55.31	$55.30	$55.30
Purchase #3	$65.36	9.104%	$71.3104	$71.31	$71.30	$71.30
Purchase #4	$248.39	9.819%	$272.7794	$272.78	$272.80	$272.80
Purchase #5	$28.52	4.784%	$29.8844	$29.88	$29.90	$29.90
Purchase #6	$168.31	12.564%	$189.4565	$189.46	$189.45	$189.50
Purchase #7	$72.70	5.250%	$76.5168	$76.52	$76.50	$76.50
7 purchase totals =	$830.67		$912.9591	$912.96	$912.95	$913.00