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	$178.61	4.841%	$187.2565	$187.26	$187.25	$187.30
Purchase #2	$183.37	3.328%	$189.4726	$189.47	$189.45	$189.50
Purchase #3	$242.31	5.439%	$255.4892	$255.49	$255.50	$255.50
Purchase #4	$35.65	4.638%	$37.3034	$37.30	$37.30	$37.30
Purchase #5	$100.74	6.269%	$107.0554	$107.06	$107.05	$107.10
Purchase #6	$170.67	9.816%	$187.423	$187.42	$187.40	$187.40
Purchase #7	$62.90	12.513%	$70.7707	$70.77	$70.75	$70.80
7 purchase totals =	$974.25		$1,034.7708	$1,034.77	$1,034.70	$1,034.90