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	$160.81	12.363%	$180.6909	$180.69	$180.70	$180.70
Purchase #2	$195.74	8.332%	$212.0491	$212.05	$212.05	$212.00
Purchase #3	$151.75	9.583%	$166.2922	$166.29	$166.30	$166.30
Purchase #4	$216.40	4.384%	$225.887	$225.89	$225.90	$225.90
Purchase #5	$66.37	9.822%	$72.8889	$72.89	$72.90	$72.90
Purchase #6	$29.56	10.123%	$32.5524	$32.55	$32.55	$32.60
Purchase #7	$163.44	13.585%	$185.6433	$185.64	$185.65	$185.60
7 purchase totals =	$984.07		$1,076.0038	$1,076.00	$1,076.05	$1,076.00