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	$52.55	6.108%	$55.7598	$55.76	$55.75	$55.80
Purchase #2	$190.59	10.726%	$211.0327	$211.03	$211.05	$211.00
Purchase #3	$210.54	4.448%	$219.9048	$219.90	$219.90	$219.90
Purchase #4	$85.42	5.870%	$90.4342	$90.43	$90.45	$90.40
Purchase #5	$50.76	3.364%	$52.4676	$52.47	$52.45	$52.50
Purchase #6	$250.61	9.694%	$274.9041	$274.90	$274.90	$274.90
Purchase #7	$46.75	6.108%	$49.6055	$49.61	$49.60	$49.60
7 purchase totals =	$887.22		$954.1087	$954.10	$954.10	$954.10