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	$162.76	13.673%	$185.0142	$185.01	$185.00	$185.00
Purchase #2	$118.79	12.838%	$134.0403	$134.04	$134.05	$134.00
Purchase #3	$54.64	4.631%	$57.1704	$57.17	$57.15	$57.20
Purchase #4	$240.90	13.821%	$274.1948	$274.19	$274.20	$274.20
Purchase #5	$87.97	4.209%	$91.6727	$91.67	$91.65	$91.70
Purchase #6	$119.28	3.660%	$123.6456	$123.65	$123.65	$123.60
Purchase #7	$158.76	13.185%	$179.6925	$179.69	$179.70	$179.70
7 purchase totals =	$943.10		$1,045.4305	$1,045.42	$1,045.40	$1,045.40