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	$104.85	10.193%	$115.5374	$115.54	$115.55	$115.50
Purchase #2	$71.61	9.548%	$78.4473	$78.45	$78.45	$78.40
Purchase #3	$16.57	5.627%	$17.5024	$17.50	$17.50	$17.50
Purchase #4	$213.48	12.499%	$240.1629	$240.16	$240.15	$240.20
Purchase #5	$164.60	8.519%	$178.6223	$178.62	$178.60	$178.60
Purchase #6	$46.65	10.365%	$51.4853	$51.49	$51.50	$51.50
Purchase #7	$51.62	4.277%	$53.8278	$53.83	$53.85	$53.80
7 purchase totals =	$669.38		$735.5854	$735.59	$735.60	$735.50