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	$108.86	4.471%	$113.7271	$113.73	$113.75	$113.70
Purchase #2	$59.52	10.273%	$65.6345	$65.63	$65.65	$65.60
Purchase #3	$112.54	4.761%	$117.898	$117.90	$117.90	$117.90
Purchase #4	$116.51	9.377%	$127.4351	$127.44	$127.45	$127.40
Purchase #5	$138.93	8.436%	$150.6501	$150.65	$150.65	$150.70
Purchase #6	$142.33	8.557%	$154.5092	$154.51	$154.50	$154.50
Purchase #7	$199.85	13.757%	$227.3434	$227.34	$227.35	$227.30
7 purchase totals =	$878.54		$957.1974	$957.20	$957.25	$957.10