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	$134.46	7.417%	$144.4329	$144.43	$144.45	$144.40
Purchase #2	$146.75	11.452%	$163.5558	$163.56	$163.55	$163.60
Purchase #3	$169.30	3.713%	$175.5861	$175.59	$175.60	$175.60
Purchase #4	$221.66	13.649%	$251.9144	$251.91	$251.90	$251.90
Purchase #5	$199.76	6.771%	$213.2857	$213.29	$213.30	$213.30
Purchase #6	$76.40	8.334%	$82.7672	$82.77	$82.75	$82.80
Purchase #7	$88.39	13.786%	$100.5754	$100.58	$100.60	$100.60
7 purchase totals =	$1,036.72		$1,132.1175	$1,132.13	$1,132.15	$1,132.20