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	$90.82	13.778%	$103.3332	$103.33	$103.35	$103.30
Purchase #2	$151.64	4.638%	$158.6731	$158.67	$158.65	$158.70
Purchase #3	$243.32	8.786%	$264.6981	$264.70	$264.70	$264.70
Purchase #4	$238.65	6.303%	$253.6921	$253.69	$253.70	$253.70
Purchase #5	$113.33	10.316%	$125.0211	$125.02	$125.00	$125.00
Purchase #6	$10.53	8.856%	$11.4625	$11.46	$11.45	$11.50
Purchase #7	$130.26	10.197%	$143.5426	$143.54	$143.55	$143.50
7 purchase totals =	$978.55		$1,060.4227	$1,060.41	$1,060.40	$1,060.40