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	$216.52	10.317%	$238.8584	$238.86	$238.85	$238.90
Purchase #2	$78.56	3.788%	$81.5359	$81.54	$81.55	$81.50
Purchase #3	$245.96	5.856%	$260.3634	$260.36	$260.35	$260.40
Purchase #4	$148.83	12.703%	$167.7359	$167.74	$167.75	$167.70
Purchase #5	$181.69	4.501%	$189.8679	$189.87	$189.85	$189.90
Purchase #6	$112.46	6.725%	$120.0229	$120.02	$120.00	$120.00
Purchase #7	$101.39	11.127%	$112.6717	$112.67	$112.65	$112.70
7 purchase totals =	$1,085.41		$1,171.0561	$1,171.06	$1,171.00	$1,171.10