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	$72.85	12.748%	$82.1369	$82.14	$82.15	$82.10
Purchase #2	$130.72	10.275%	$144.1515	$144.15	$144.15	$144.20
Purchase #3	$169.38	5.339%	$178.4232	$178.42	$178.40	$178.40
Purchase #4	$250.34	5.207%	$263.3752	$263.38	$263.40	$263.40
Purchase #5	$11.92	5.769%	$12.6077	$12.61	$12.60	$12.60
Purchase #6	$124.68	12.662%	$140.467	$140.47	$140.45	$140.50
Purchase #7	$240.48	12.867%	$271.4226	$271.42	$271.40	$271.40
7 purchase totals =	$1,000.37		$1,092.5841	$1,092.59	$1,092.55	$1,092.60