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	$111.39	8.287%	$120.6209	$120.62	$120.60	$120.60
Purchase #2	$220.79	10.450%	$243.8626	$243.86	$243.85	$243.90
Purchase #3	$88.59	3.857%	$92.0069	$92.01	$92.00	$92.00
Purchase #4	$89.41	5.550%	$94.3723	$94.37	$94.35	$94.40
Purchase #5	$13.91	4.712%	$14.5654	$14.57	$14.55	$14.60
Purchase #6	$231.78	10.135%	$255.2709	$255.27	$255.25	$255.30
Purchase #7	$248.58	9.426%	$272.0112	$272.01	$272.00	$272.00
7 purchase totals =	$1,004.45		$1,092.7102	$1,092.71	$1,092.60	$1,092.80