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	$124.54	11.347%	$138.6716	$138.67	$138.65	$138.70
Purchase #2	$14.72	3.719%	$15.2674	$15.27	$15.25	$15.30
Purchase #3	$189.69	12.534%	$213.4657	$213.47	$213.45	$213.50
Purchase #4	$209.69	5.407%	$221.0279	$221.03	$221.05	$221.00
Purchase #5	$210.30	3.703%	$218.0874	$218.09	$218.10	$218.10
Purchase #6	$240.39	9.233%	$262.5852	$262.59	$262.60	$262.60
Purchase #7	$52.63	12.732%	$59.3309	$59.33	$59.35	$59.30
7 purchase totals =	$1,041.96		$1,128.4361	$1,128.45	$1,128.45	$1,128.50