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	$43.97	3.517%	$45.5164	$45.52	$45.50	$45.50
Purchase #2	$39.45	8.853%	$42.9425	$42.94	$42.95	$42.90
Purchase #3	$62.42	5.509%	$65.8587	$65.86	$65.85	$65.90
Purchase #4	$30.79	12.188%	$34.5427	$34.54	$34.55	$34.50
Purchase #5	$93.43	6.623%	$99.6179	$99.62	$99.60	$99.60
Purchase #6	$197.35	8.228%	$213.588	$213.59	$213.60	$213.60
Purchase #7	$231.28	11.680%	$258.2935	$258.29	$258.30	$258.30
7 purchase totals =	$698.69		$760.3597	$760.36	$760.35	$760.30