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	$158.92	6.382%	$169.0623	$169.06	$169.05	$169.10
Purchase #2	$88.59	3.694%	$91.8625	$91.86	$91.85	$91.90
Purchase #3	$120.85	9.386%	$132.193	$132.19	$132.20	$132.20
Purchase #4	$77.38	10.466%	$85.4786	$85.48	$85.50	$85.50
Purchase #5	$189.42	8.146%	$204.8502	$204.85	$204.85	$204.90
Purchase #6	$143.88	7.425%	$154.5631	$154.56	$154.55	$154.60
Purchase #7	$200.70	8.570%	$217.9	$217.90	$217.90	$217.90
7 purchase totals =	$979.74		$1,055.9097	$1,055.90	$1,055.90	$1,056.10