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	$123.30	6.305%	$131.0741	$131.07	$131.05	$131.10
Purchase #2	$13.92	6.844%	$14.8727	$14.87	$14.85	$14.90
Purchase #3	$185.44	12.693%	$208.9779	$208.98	$209.00	$209.00
Purchase #4	$38.38	8.184%	$41.521	$41.52	$41.50	$41.50
Purchase #5	$62.94	5.734%	$66.549	$66.55	$66.55	$66.50
Purchase #6	$104.64	10.299%	$115.4169	$115.42	$115.40	$115.40
Purchase #7	$149.84	12.467%	$168.5206	$168.52	$168.50	$168.50
7 purchase totals =	$678.46		$746.9322	$746.93	$746.85	$746.90