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	$139.54	12.437%	$156.8946	$156.89	$156.90	$156.90
Purchase #2	$158.86	6.800%	$169.6625	$169.66	$169.65	$169.70
Purchase #3	$139.75	10.505%	$154.4307	$154.43	$154.45	$154.40
Purchase #4	$140.40	10.642%	$155.3414	$155.34	$155.35	$155.30
Purchase #5	$244.90	4.310%	$255.4552	$255.46	$255.45	$255.50
Purchase #6	$65.64	4.524%	$68.6096	$68.61	$68.60	$68.60
Purchase #7	$196.68	9.679%	$215.7167	$215.72	$215.70	$215.70
7 purchase totals =	$1,085.77		$1,176.1107	$1,176.11	$1,176.10	$1,176.10