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	$55.77	5.788%	$58.998	$59.00	$59.00	$59.00
Purchase #2	$221.33	11.208%	$246.1367	$246.14	$246.15	$246.10
Purchase #3	$162.86	4.675%	$170.4737	$170.47	$170.45	$170.50
Purchase #4	$110.26	12.720%	$124.2851	$124.29	$124.30	$124.30
Purchase #5	$160.80	13.251%	$182.1076	$182.11	$182.10	$182.10
Purchase #6	$80.30	12.451%	$90.2982	$90.30	$90.30	$90.30
Purchase #7	$205.75	4.647%	$215.3112	$215.31	$215.30	$215.30
7 purchase totals =	$997.07		$1,087.6105	$1,087.62	$1,087.60	$1,087.60