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	$37.87	5.220%	$39.8468	$39.85	$39.85	$39.80
Purchase #2	$184.33	13.776%	$209.7233	$209.72	$209.70	$209.70
Purchase #3	$185.45	7.825%	$199.9615	$199.96	$199.95	$200.00
Purchase #4	$81.37	12.270%	$91.3541	$91.35	$91.35	$91.40
Purchase #5	$233.52	9.429%	$255.5386	$255.54	$255.55	$255.50
Purchase #6	$144.37	13.546%	$163.9264	$163.93	$163.95	$163.90
Purchase #7	$156.47	6.773%	$167.0677	$167.07	$167.05	$167.10
7 purchase totals =	$1,023.38		$1,127.4184	$1,127.42	$1,127.40	$1,127.40