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	$165.94	3.359%	$171.5139	$171.51	$171.50	$171.50
Purchase #2	$181.84	5.372%	$191.6084	$191.61	$191.60	$191.60
Purchase #3	$177.27	8.455%	$192.2582	$192.26	$192.25	$192.30
Purchase #4	$184.25	6.571%	$196.3571	$196.36	$196.35	$196.40
Purchase #5	$245.86	10.653%	$272.0515	$272.05	$272.05	$272.10
Purchase #6	$177.39	3.375%	$183.3769	$183.38	$183.40	$183.40
Purchase #7	$226.63	4.175%	$236.0918	$236.09	$236.10	$236.10
7 purchase totals =	$1,359.18		$1,443.2578	$1,443.26	$1,443.25	$1,443.40