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	$127.82	3.740%	$132.6005	$132.60	$132.60	$132.60
Purchase #2	$182.41	10.180%	$200.9793	$200.98	$201.00	$201.00
Purchase #3	$79.52	3.719%	$82.4773	$82.48	$82.50	$82.50
Purchase #4	$239.32	5.262%	$251.913	$251.91	$251.90	$251.90
Purchase #5	$152.64	13.688%	$173.5334	$173.53	$173.55	$173.50
Purchase #6	$98.38	10.451%	$108.6617	$108.66	$108.65	$108.70
Purchase #7	$103.50	5.761%	$109.4626	$109.46	$109.45	$109.50
7 purchase totals =	$983.59		$1,059.6278	$1,059.62	$1,059.65	$1,059.70