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	$140.41	8.866%	$152.8588	$152.86	$152.85	$152.90
Purchase #2	$178.57	9.426%	$195.402	$195.40	$195.40	$195.40
Purchase #3	$78.76	11.806%	$88.0584	$88.06	$88.05	$88.10
Purchase #4	$215.84	13.670%	$245.3453	$245.35	$245.35	$245.30
Purchase #5	$100.58	11.457%	$112.1035	$112.10	$112.10	$112.10
Purchase #6	$208.87	13.530%	$237.1301	$237.13	$237.15	$237.10
Purchase #7	$33.81	10.544%	$37.3749	$37.37	$37.35	$37.40
7 purchase totals =	$956.84		$1,068.2730	$1,068.27	$1,068.25	$1,068.30