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	$115.99	6.839%	$123.9226	$123.92	$123.90	$123.90
Purchase #2	$206.64	4.328%	$215.5834	$215.58	$215.60	$215.60
Purchase #3	$227.43	6.134%	$241.3806	$241.38	$241.40	$241.40
Purchase #4	$202.35	9.731%	$222.0407	$222.04	$222.05	$222.00
Purchase #5	$203.43	9.800%	$223.3661	$223.37	$223.35	$223.40
Purchase #6	$13.83	7.612%	$14.8827	$14.88	$14.90	$14.90
Purchase #7	$205.81	7.689%	$221.6347	$221.63	$221.65	$221.60
7 purchase totals =	$1,175.48		$1,262.8108	$1,262.80	$1,262.85	$1,262.80