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	$138.53	7.204%	$148.5097	$148.51	$148.50	$148.50
Purchase #2	$211.90	6.643%	$225.9765	$225.98	$226.00	$226.00
Purchase #3	$59.32	8.666%	$64.4607	$64.46	$64.45	$64.50
Purchase #4	$238.89	6.284%	$253.9018	$253.90	$253.90	$253.90
Purchase #5	$218.46	13.313%	$247.5436	$247.54	$247.55	$247.50
Purchase #6	$137.92	5.367%	$145.3222	$145.32	$145.30	$145.30
Purchase #7	$190.67	9.243%	$208.2936	$208.29	$208.30	$208.30
7 purchase totals =	$1,195.69		$1,294.0081	$1,294.00	$1,294.00	$1,294.00