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	$198.56	8.312%	$215.0643	$215.06	$215.05	$215.10
Purchase #2	$104.46	13.403%	$118.4608	$118.46	$118.45	$118.50
Purchase #3	$104.90	10.401%	$115.8106	$115.81	$115.80	$115.80
Purchase #4	$81.33	7.656%	$87.5566	$87.56	$87.55	$87.60
Purchase #5	$177.31	7.426%	$190.477	$190.48	$190.50	$190.50
Purchase #6	$191.48	10.143%	$210.9018	$210.90	$210.90	$210.90
Purchase #7	$143.72	5.631%	$151.8129	$151.81	$151.80	$151.80
7 purchase totals =	$1,001.76		$1,090.0840	$1,090.08	$1,090.05	$1,090.20