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	$152.25	4.588%	$159.2352	$159.24	$159.25	$159.20
Purchase #2	$54.62	9.112%	$59.597	$59.60	$59.60	$59.60
Purchase #3	$202.86	5.232%	$213.4736	$213.47	$213.45	$213.50
Purchase #4	$106.92	10.253%	$117.8825	$117.88	$117.90	$117.90
Purchase #5	$96.57	9.752%	$105.9875	$105.99	$106.00	$106.00
Purchase #6	$143.27	6.647%	$152.7932	$152.79	$152.80	$152.80
Purchase #7	$240.61	6.591%	$256.4686	$256.47	$256.45	$256.50
7 purchase totals =	$997.10		$1,065.4376	$1,065.44	$1,065.45	$1,065.50