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	$185.42	5.573%	$195.7535	$195.75	$195.75	$195.80
Purchase #2	$240.43	6.649%	$256.4162	$256.42	$256.40	$256.40
Purchase #3	$206.72	7.209%	$221.6224	$221.62	$221.60	$221.60
Purchase #4	$128.95	9.420%	$141.0971	$141.10	$141.10	$141.10
Purchase #5	$242.45	10.565%	$268.0648	$268.06	$268.05	$268.10
Purchase #6	$148.66	13.385%	$168.5581	$168.56	$168.55	$168.60
Purchase #7	$137.27	9.581%	$150.4218	$150.42	$150.40	$150.40
7 purchase totals =	$1,289.90		$1,401.9339	$1,401.93	$1,401.85	$1,402.00