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	$99.61	6.276%	$105.8615	$105.86	$105.85	$105.90
Purchase #2	$23.45	13.255%	$26.5583	$26.56	$26.55	$26.60
Purchase #3	$128.29	3.541%	$132.8327	$132.83	$132.85	$132.80
Purchase #4	$62.46	6.432%	$66.4774	$66.48	$66.50	$66.50
Purchase #5	$93.76	12.480%	$105.4612	$105.46	$105.45	$105.50
Purchase #6	$81.87	10.170%	$90.1962	$90.20	$90.20	$90.20
Purchase #7	$173.54	13.273%	$196.574	$196.57	$196.55	$196.60
7 purchase totals =	$662.98		$723.9613	$723.96	$723.95	$724.10