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	$144.96	5.636%	$153.1299	$153.13	$153.15	$153.10
Purchase #2	$43.38	8.291%	$46.9766	$46.98	$47.00	$47.00
Purchase #3	$199.54	10.872%	$221.234	$221.23	$221.25	$221.20
Purchase #4	$222.85	12.419%	$250.5257	$250.53	$250.55	$250.50
Purchase #5	$196.56	10.810%	$217.8081	$217.81	$217.80	$217.80
Purchase #6	$104.73	12.226%	$117.5343	$117.53	$117.55	$117.50
Purchase #7	$66.94	9.570%	$73.3462	$73.35	$73.35	$73.30
7 purchase totals =	$978.96		$1,080.5548	$1,080.56	$1,080.65	$1,080.40