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	$235.52	12.687%	$265.4004	$265.40	$265.40	$265.40
Purchase #2	$73.96	6.395%	$78.6897	$78.69	$78.70	$78.70
Purchase #3	$196.47	13.372%	$222.742	$222.74	$222.75	$222.70
Purchase #4	$162.61	12.754%	$183.3493	$183.35	$183.35	$183.30
Purchase #5	$43.71	9.383%	$47.8113	$47.81	$47.80	$47.80
Purchase #6	$6.51	13.699%	$7.4018	$7.40	$7.40	$7.40
Purchase #7	$148.63	5.167%	$156.3097	$156.31	$156.30	$156.30
7 purchase totals =	$867.41		$961.7042	$961.70	$961.70	$961.60