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	$136.27	3.345%	$140.8282	$140.83	$140.85	$140.80
Purchase #2	$140.37	5.838%	$148.5648	$148.56	$148.55	$148.60
Purchase #3	$210.88	4.841%	$221.0887	$221.09	$221.10	$221.10
Purchase #4	$50.41	6.317%	$53.5944	$53.59	$53.60	$53.60
Purchase #5	$132.94	11.661%	$148.4421	$148.44	$148.45	$148.40
Purchase #6	$212.62	13.647%	$241.6363	$241.64	$241.65	$241.60
Purchase #7	$132.55	5.797%	$140.2339	$140.23	$140.25	$140.20
7 purchase totals =	$1,016.04		$1,094.3884	$1,094.38	$1,094.45	$1,094.30