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	$102.76	5.755%	$108.6738	$108.67	$108.65	$108.70
Purchase #2	$245.85	4.743%	$257.5107	$257.51	$257.50	$257.50
Purchase #3	$151.60	7.184%	$162.4909	$162.49	$162.50	$162.50
Purchase #4	$45.34	9.126%	$49.4777	$49.48	$49.50	$49.50
Purchase #5	$71.71	12.429%	$80.6228	$80.62	$80.60	$80.60
Purchase #6	$89.29	8.544%	$96.9189	$96.92	$96.90	$96.90
Purchase #7	$239.46	8.713%	$260.3241	$260.32	$260.30	$260.30
7 purchase totals =	$946.01		$1,016.0189	$1,016.01	$1,015.95	$1,016.00