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	$64.30	10.515%	$71.0611	$71.06	$71.05	$71.10
Purchase #2	$97.43	3.407%	$100.7494	$100.75	$100.75	$100.70
Purchase #3	$6.45	6.149%	$6.8466	$6.85	$6.85	$6.80
Purchase #4	$31.47	4.534%	$32.8968	$32.90	$32.90	$32.90
Purchase #5	$200.83	3.235%	$207.3269	$207.33	$207.35	$207.30
Purchase #6	$105.52	5.672%	$111.5051	$111.51	$111.50	$111.50
Purchase #7	$14.59	7.385%	$15.6675	$15.67	$15.65	$15.70
7 purchase totals =	$520.59		$546.0534	$546.07	$546.05	$546.00