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	$144.42	12.291%	$162.1707	$162.17	$162.15	$162.20
Purchase #2	$28.83	9.487%	$31.5651	$31.57	$31.55	$31.60
Purchase #3	$134.85	8.453%	$146.2489	$146.25	$146.25	$146.20
Purchase #4	$166.81	10.656%	$184.5853	$184.59	$184.60	$184.60
Purchase #5	$156.77	12.235%	$175.9508	$175.95	$175.95	$176.00
Purchase #6	$241.39	10.417%	$266.5356	$266.54	$266.55	$266.50
Purchase #7	$85.52	9.384%	$93.5452	$93.55	$93.55	$93.50
7 purchase totals =	$958.59		$1,060.6016	$1,060.62	$1,060.60	$1,060.60