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	$153.28	7.313%	$164.4894	$164.49	$164.50	$164.50
Purchase #2	$118.60	4.832%	$124.3308	$124.33	$124.35	$124.30
Purchase #3	$104.51	4.544%	$109.2589	$109.26	$109.25	$109.30
Purchase #4	$144.60	6.191%	$153.5522	$153.55	$153.55	$153.60
Purchase #5	$28.51	11.270%	$31.7231	$31.72	$31.70	$31.70
Purchase #6	$225.98	12.137%	$253.4072	$253.41	$253.40	$253.40
Purchase #7	$222.45	5.564%	$234.8271	$234.83	$234.85	$234.80
7 purchase totals =	$997.93		$1,071.5887	$1,071.59	$1,071.60	$1,071.60